UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of the

Securities Exchange Act of 1934

Filed by the Registrant ☒

Filed by a Party other than the Registrant ☐

Check the appropriate box:

Summit Financial Group, Inc.

(Name of Registrant as Specified in its Charter)

(Name of Person(s) Filing Proxy Statement, if other than the Registrant)

Payment of Filing Fee (Check all boxes that apply):

To the Shareholders of Burke & Herbert Financial Services Corp. and Summit Financial Group, Inc.

MERGER PROPOSED—YOUR VOTE IS VERY IMPORTANT

On behalf of the boards of directors of Burke & Herbert Financial Services Corp. (“Burke & Herbert”) and Summit Financial Group, Inc. (“Summit”), we are pleased to enclose the accompanying joint proxy statement/prospectus relating to the proposed combination of Burke & Herbert and Summit. We are requesting that you take certain actions as a holder of Burke & Herbert common stock (a “Burke & Herbert shareholder”) or as a holder of Summit common stock (a “Summit shareholder”).

On August 24, 2023, Burke & Herbert and Summit entered into an Agreement and Plan of Reorganization and accompanying Plan of Merger (as may be amended, modified or supplemented from time to time in accordance with its terms, the “merger agreement”), pursuant to which Summit will merge with and into Burke & Herbert, with Burke & Herbert as the continuing corporation (the “merger”). Immediately following the merger, Summit Community Bank, Inc., a West Virginia banking corporation (“SCB”) and a wholly-owned direct subsidiary of Summit, will merge with and into Burke & Herbert Bank & Trust Company, a Virginia banking corporation (“B&H Bank”) and a wholly-owned direct subsidiary of Burke & Herbert, with B&H Bank as the continuing bank (the “bank merger,” and together with the merger, the “mergers”).

In the merger, Summit shareholders will receive 0.5043 shares of Burke & Herbert common stock for each share of Summit common stock they own (the “exchange ratio”), subject to the payment of cash in lieu of fractional shares (“merger consideration”). Based on the $49.98 closing price of Burke & Herbert’s common stock on the Nasdaq Stock Market LLC (“Nasdaq”) on August 23, 2023, the last day before the public announcement of the merger, the exchange ratio represented approximately $25.20 in value for each share of Summit common stock, representing merger consideration of approximately $371.5 million on an aggregate basis. Based on the $46.54 closing price of Burke & Herbert common stock on Nasdaq on October 12, 2023 the latest practicable trading day before the printing of the accompanying joint proxy statement/prospectus, the exchange ratio represented approximately $23.47 in value for each share of Summit common stock, representing merger consideration of approximately $345.0 million on an aggregate basis.

In addition, each share of Summit series 2021 preferred stock issued and outstanding immediately prior to the effective time of the merger will be converted into the right to receive one share of a newly created series of Burke & Herbert preferred stock having rights, preferences, privileges and voting powers and limitations and restrictions thereof that are not materially less or more favorable to the holders of the Summit series 2021 preferred stock.

Burke & Herbert shareholders will continue to own their existing shares of Burke & Herbert common stock. The value of the Burke & Herbert common stock at the time of completion of the merger could be greater than, less than or the same as the value of Burke & Herbert common stock on the date of the accompanying joint proxy statement/prospectus. We urge you to obtain current market quotations of Burke & Herbert common stock (Nasdaq trading symbol “BHRB”) and Summit common stock (Nasdaq trading symbol “SMMF”).

The merger is intended to qualify as a reorganization for federal income tax purposes. Accordingly, Summit shareholders generally will not recognize any gain or loss for federal income tax purposes on the exchange of shares of Summit common

stock for Burke & Herbert common stock in the merger, except with respect to any cash received by such holders in lieu of fractional shares of Burke & Herbert common stock.

Based on the exchange ratio and the number of shares of Summit common stock outstanding as of October 12, 2023, Burke & Herbert expects to issue approximately 7,400,527 shares of Burke & Herbert common stock to Summit shareholders in the aggregate in the merger. We estimate that former Summit shareholders will own approximately 50% and existing Burke & Herbert shareholders will own approximately 50% of the common stock of Burke & Herbert following the completion of the merger.

Burke & Herbert and Summit will each hold a special meeting of its respective common stock shareholders in connection with the merger. At their respective special meetings, in addition to other business, Burke & Herbert and Summit will ask their respective shareholders to approve the merger agreement. Information about these meetings and the mergers is contained in this document. We urge you to read this document carefully and in its entirety. Holders of Summit series 2021 preferred stock are not entitled to, and are not requested to, vote at the Summit special meeting.

The special meeting of Summit shareholders will be held on December 6, 2023 at 1:00 p.m., Eastern Time at Summit’s corporate office located at 300 North Main Street, Moorefield, WV 26836. The special meeting of Burke & Herbert shareholders will be held virtually via the internet on December 6, 2023 at 8:00 a.m., Eastern Time.

Each of the Burke & Herbert and Summit boards of directors unanimously recommends that holders of common stock vote “FOR” each of the proposals to be considered at the respective meetings. We strongly support this combination of our companies and join our boards in their recommendations.

This joint proxy statement/prospectus provides you with detailed information about the merger agreement and the mergers. It also contains or references information about Burke  & Herbert and Summit and certain related matters. You are encouraged to read this joint proxy statement/prospectus carefully. In particular, you should read the “Risk Factors” section beginning on page 32 for a discussion of the risks you should consider in evaluating the proposed merger and how it will affect you. You can also obtain information about Summit from documents that have been filed with the Securities and Exchange Commission that are incorporated into this joint proxy statement/prospectus by reference.

On behalf of the Burke & Herbert and Summit boards of directors, thank you for your prompt attention to this important matter.

Sincerely,

David P. Boyle President and Chief Executive Officer Burke & Herbert Financial Services Corp.		H. Charles Maddy, III President and Chief Executive Officer Summit Financial Group, Inc.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of the securities to be issued in connection with the merger or determined if this document is accurate or complete. Any representation to the contrary is a criminal offense.

The securities to be issued in the merger are not savings or deposit accounts or other obligations of any bank or non-bank subsidiary of either Burke & Herbert or Summit, and they are not insured by the Federal Deposit Insurance Corporation or any other governmental agency.

The accompanying joint proxy statement/prospectus is dated October 16, 2023, and is first being mailed or otherwise delivered to holders of Burke & Herbert common stock and holders of Summit common stock on or about October 19, 2023.

ADDITIONAL INFORMATION

The accompanying joint proxy statement/prospectus incorporates important business and financial information about Summit from other documents that are not included in or delivered with this document. This information is available to you without charge upon your written or oral request. You can obtain the documents incorporated by reference in this document through the Securities and Exchange Commission website at www.sec.gov. You will also be able to obtain these documents free of charge from Burke & Herbert by accessing Burke & Herbert’s website at www.burkeandherbertbank.com under the “Investor Relations” link or at Summit’s website at www.summitfgi.com under the “News / News and Filings” link. You may also request these documents in writing, by email or by telephone, at the appropriate address below:

You will not be charged for any of these documents that you request. To obtain timely delivery of these documents, you must request them no later than five business days before the date of the applicable special meeting. This means that holders of Burke & Herbert common stock requesting documents must do so by November 29, 2023, in order to receive them before the Burke & Herbert special meeting; holders of Summit common stock requesting documents must do so by November 29, 2023, in order to receive them before the Summit special meeting.

No one has been authorized to provide you with information that is different from that contained in, or incorporated by reference into, this document. This document is dated October 16, 2023, and you should assume that the information in this document is accurate only as of such date. You should assume that the information incorporated by reference into this document is accurate as of the date of such incorporated document. Neither the mailing of this document to holders of Burke & Herbert common stock or holders of Summit common stock, nor the issuance by Burke & Herbert of shares of Burke & Herbert common stock pursuant to the merger agreement will create any implication to the contrary.

The information on Burke & Herbert’s and Summit’s websites is not part of this document. References to Burke & Herbert’s and Summit’s websites in this document are intended to serve as textual references only.

This document does not constitute an offer to sell, or a solicitation of an offer to buy, any securities, or the solicitation of a proxy, in any jurisdiction to or from any person to whom it is unlawful to make any such offer or solicitation in such jurisdiction. Except where the context otherwise indicates, information contained in this document regarding Burke & Herbert has been provided by Burke & Herbert and information contained in, or incorporated by reference into, this document regarding Summit has been provided by Summit.

See “Where You Can Find More Information” beginning on page 176 of the accompanying joint proxy statement/prospectus for further information.

Burke & Herbert Financial Services Corp.

100 S. Fairfax Street

Alexandria, VA 22314

NOTICE OF SPECIAL MEETING OF BURKE & HERBERT SHAREHOLDERS

To Burke & Herbert Financial Services Corp. shareholders:

On August 24, 2023, Burke & Herbert Financial Services Corp. (“Burke & Herbert”) and Summit Financial Group, Inc. (“Summit”) entered into an Agreement and Plan of Reorganization and accompanying Plan of Merger (as may be amended, modified or supplemented from time to time in accordance with its terms, the “merger agreement”). A copy of the merger agreement is attached as Annex A to the accompanying joint proxy statement/prospectus.

NOTICE IS HEREBY GIVEN that a special meeting of holders of Burke & Herbert common stock (the “Burke & Herbert special meeting”) will be held on December 6, 2023 at 8:00 a.m., Eastern Time. We are pleased to notify you of, and invite you to, the Burke & Herbert special meeting, which will be held virtually via the internet.

At the Burke & Herbert special meeting you will be asked to vote on the following matters:

The Burke & Herbert special meeting will be held in a virtual-only format conducted via live webcast. As more fully described in the “Questions & Answers” and “The Burke & Herbert Special Meeting” sections of the accompanying joint proxy statement/prospectus, you are entitled to participate in the Burke & Herbert special meeting if, as of the close of business on October 12, 2023, you held shares of Burke & Herbert common stock registered in your name (a “record holder”), or if you held shares through a bank, broker, trustee or other nominee (a “beneficial owner”). Record holders will be able to attend the Burke & Herbert special meeting online, ask questions and vote during the meeting by visiting https://web.lumiagm.com/261284453 and following the instructions. The password for the meeting, if requested, is burke 2023. Please have your control number, which can be found on your notice, proxy card or voting instruction form, to access the meeting. If you are a beneficial owner, have a valid proxy for the Burke & Herbert special meeting and register beforehand, you also will be able to attend the Burke & Herbert special meeting online, ask questions and vote during the meeting. See the “Questions & Answers” section of the accompanying joint proxy statement/prospectus for more information, including technical support information for the virtual Burke & Herbert special meeting.

The board of directors of Burke & Herbert has fixed the close of business on October 12, 2023 as the record date for the Burke & Herbert special meeting. Only holders of record of Burke & Herbert common stock as of the

close of business on the record date for the Burke & Herbert special meeting are entitled to notice of the Burke & Herbert special meeting or any adjournment or postponement thereof. Only holders of record of Burke & Herbert common stock will be entitled to vote at the Burke & Herbert special meeting or any adjournment or postponement thereof.

Burke & Herbert has determined that holders of Burke & Herbert common stock are not entitled to appraisal rights with respect to the proposed merger under the Virginia Stock Corporation Act, as amended.

The Burke & Herbert board of directors unanimously recommends that holders of Burke & Herbert common stock vote “FOR” the Burke & Herbert merger proposal and “FOR” the Burke & Herbert adjournment proposal.

Your vote is important! We cannot complete the transactions contemplated by the merger agreement unless holders of Burke & Herbert common stock approve the Burke & Herbert merger proposal. The affirmative vote of a majority of the votes entitled to be cast by the holders of outstanding shares of Burke & Herbert common stock at the Burke & Herbert special meeting is required to approve the Burke & Herbert merger. Whether or not you plan to attend the Burke & Herbert special meeting, we urge you to please promptly complete, sign, date and return the accompanying proxy card in the enclosed postage-paid envelope or authorize the individuals named on the accompanying proxy card to vote your shares by calling the toll-free telephone number or by using the internet as described in the instructions included with the accompanying proxy card. If your shares are held in the name of a bank, broker or other nominee, please follow the instructions on the voting instruction card furnished by such bank, broker or other nominee.

		By Order of the Board of Directors
		David P. Boyle President and Chief Executive Officer Burke & Herbert Financial Services Corp.
October 16, 2023

Summit Financial Group, Inc.

300 N. Main Street

Moorefield, WV 26836

NOTICE OF SPECIAL MEETING OF SUMMIT SHAREHOLDERS

To Summit Financial Group, Inc. Shareholders:

On August 24, 2023, Burke & Herbert Financial Services Corp. (“Burke & Herbert”) and Summit Financial Group, Inc. (“Summit”) entered into an Agreement and Plan of Reorganization and accompanying Plan of Merger (as may be amended, modified or supplemented from time to time in accordance with its terms, the “merger agreement”). A copy of the merger agreement is attached as Annex A to the accompanying joint proxy statement/prospectus.

NOTICE IS HEREBY GIVEN that a special meeting of holders of Summit common stock (the “Summit special meeting”) will be held on December 6, 2023 at 1:00 p.m., Eastern Time. We are pleased to notify you of and invite you to the Summit special meeting which will be held at Summit’s corporate office located at 300 North Main Street, Moorefield, WV 26836.

At the Summit special meeting, holders of Summit common stock will be asked to vote on the following matters:

The Summit special meeting will be held at Summit’s corporate office located at 300 North Main Street, Moorefield, WV 26836. As more fully described in the “Questions & Answers” and “The Summit Special Meeting” sections of the accompanying joint proxy statement/prospectus, you are entitled to participate in the Summit special meeting if, as of the close of business on October 12, 2023, you held shares of Summit common stock registered in your name (a “record holder”), or if you held shares through a bank, broker, trustee or other nominee (a “beneficial owner”). Record holders will be able to attend the Summit special meeting, ask questions and vote during the meeting. If you are a beneficial owner and have a valid proxy for the Summit special meeting, you also will be able to attend the Summit special meeting, ask questions and vote during the meeting. See the “Questions & Answers” section of the accompanying joint proxy statement/prospectus for more information about Summit’s special meeting.

The board of directors of Summit has fixed the close of business on October 12, 2023 as the record date for the Summit special meeting. Only holders of record of Summit common stock as of the close of business on the record date for the Summit special meeting are entitled to notice of the Summit special meeting or any adjournment or

postponement thereof. Only holders of record of Summit common stock will be entitled to vote at the Summit special meeting or any adjournment or postponement thereof. Holders of Summit series 2021 preferred stock are not entitled to, and are not requested to, vote at the Summit special meeting.

Summit has determined that holders of Summit common stock are not entitled to appraisal rights with respect to the proposed merger under the West Virginia Business Corporation Act, as amended.

The Summit board of directors has unanimously adopted and approved the merger and the merger agreement and unanimously recommends that holders of Summit common stock vote “FOR” the Summit merger proposal, “FOR” the Summit compensation proposal and “FOR” the Summit adjournment proposal.

Your vote is important! We cannot complete the transactions contemplated by the merger agreement unless holders of Summit common stock approve the Summit merger proposal. The affirmative vote of a majority of the votes entitled to be cast at the special meeting by the holders of outstanding shares of Summit common stock at the special meeting is required to approve the Summit merger proposal. Whether or not you plan to attend the Summit special meeting, we urge you to please promptly complete, sign, date and return the accompanying proxy card in the enclosed postage-paid envelope or authorize the individuals named on the accompanying proxy card to vote your shares by calling the toll-free telephone number or by using the internet as described in the instructions included with the accompanying proxy card. If your shares are held in the name of a bank, broker or other nominee, please follow the instructions on the voting instruction card furnished by such bank, broker or other nominee.

		By Order of the Board of Directors
		H. Charles Maddy, III President and Chief Executive Officer Summit Financial Group, Inc.
October 16, 2023

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RISK FACTORS

In addition to the other information contained in or incorporated by reference into this joint proxy statement/prospectus, including the matters addressed under the caption “Cautionary Statement Regarding Forward-Looking Statements” beginning on page 29, Burke & Herbert shareholders should carefully consider the following risk factors in deciding whether to vote for the approval of the Burke & Herbert merger proposal and Summit shareholders should carefully consider the following risk factors in deciding whether to vote for the approval of the Summit merger proposal. In addition, Burke & Herbert and Summit have discussed certain other material risks connected with the ownership of Burke & Herbert common stock and with Burke & Herbert’s business, and with the ownership of Summit common stock and Summit’s business, respectively, under the caption “Risk Factors” appearing in, for Burke & Herbert, its Registration Statement on Form 10, as amended and declared effective on April 21, 2023 (the “Burke & Herbert Form 10 registration statement”), attached as Annex D, and, for Summit, in its Annual Reports on Form 10-K for the year ended December 31, 2022, and may include additional or updated disclosures of such material risks in their subsequent Quarterly Reports on Form 10-Q and Current Reports on Form 8-K that each has filed with the SEC or may file with the SEC after the date of this joint proxy statement/prospectus.

Burke & Herbert shareholders and Summit shareholders should carefully read and consider all of these risks and all other information contained in this joint proxy statement/prospectus, including the discussions of risk factors included in the documents incorporated by reference into or attached hereto as annexes to this joint proxy statement/prospectus, in deciding whether to vote for approval of the various proposals for which they may be entitled to vote at the Burke & Herbert special meeting or the Summit special meeting. The risks described in this joint proxy statement/prospectus and in those documents incorporated by reference herein or attached as annexes hereto may adversely affect the value of Burke & Herbert common stock that you, as an existing Burke & Herbert shareholder, currently hold or that you, as an existing Summit shareholder, will hold upon consummation of the merger, and could result in a significant decline in the value of Burke & Herbert common stock and cause Burke & Herbert shareholders and/or Summit shareholders to lose all or part of the value of their respective investments in Burke & Herbert common stock.

Risks Relating to the Consummation of the Merger and Burke & Herbert Following the Merger

Because the market price of Burke & Herbert common stock may fluctuate, Summit shareholders cannot be certain of the market value of the merger consideration they will receive.

In the merger, each share of Summit common stock issued and outstanding immediately prior to the effective time, except for shares of Summit common stock owned by Summit as treasury stock or owned by Summit or Burke & Herbert (in each case, other than shares of Summit common stock (i) held in any employee benefit plans, trust accounts, managed accounts, mutual funds and the like, or otherwise held in a fiduciary or agency capacity that are beneficially owned by third parties, or (ii) held, directly or indirectly, by Summit or Burke & Herbert in respect of debts previously contracted), will be converted into 0.5043 shares of Burke & Herbert common stock. This exchange ratio is fixed and will not be adjusted for changes in the market price of either Burke & Herbert common stock or Summit common stock. Changes in the price of Burke & Herbert common stock between now and the time of the merger will affect the value that Summit shareholders will receive in the merger. Neither Burke & Herbert nor Summit is permitted to terminate the merger agreement as a result of any increase or decrease in the market price of Burke & Herbert common stock or Summit common stock.

Stock price changes may result from a variety of factors, including general market and economic conditions, changes in Burke & Herbert’s and Summit’s businesses, operations and prospects, the recent volatility in the prices of securities in global financial markets, including market prices of Burke & Herbert, Summit and other banking companies, the effects of the COVID-19 pandemic and regulatory considerations and tax laws, many of which are beyond Burke & Herbert’s and Summit’s control. Therefore, at the time of the Burke & Herbert special meeting and the Summit special meeting, Burke & Herbert shareholders and Summit shareholders will not know the market value of the consideration that Summit shareholders will receive at the effective time. You should obtain current market quotations for shares of Burke & Herbert common stock (Nasdaq: BHRB) and for shares of Summit common stock (Nasdaq: SMMF).

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The market price of Burke & Herbert common stock after the merger may be affected by factors different from those currently affecting the shares of Burke & Herbert common stock or Summit common stock.

In the merger, Summit shareholders will become Burke & Herbert shareholders. Burke & Herbert’s business differs from that of Summit and certain adjustments may be made to Burke & Herbert’s business as a result of the merger. Accordingly, the results of operations of the continuing corporation and the market price of Burke & Herbert common stock after the completion of the merger may be affected by factors different from those currently affecting the independent results of operations of each of Burke & Herbert and Summit. For a discussion of the businesses, and certain factors to consider in connection with those businesses, of Burke & Herbert see “Risk Factors—Risks Related to Burke & Herbert’s Business” and for Summit see the documents incorporated by reference in this joint proxy statement/prospectus and referred to under “Where You Can Find More Information” beginning on page 176.

The opinion delivered by KBW to Burke & Herbert’s board of directors and the opinion delivered by D.A. Davidson to Summit’s board of directors, respectively, prior to the entry into the merger agreement will not reflect changes in circumstances that may have occurred since the dates of the opinions.

The opinion from KBW, Burke & Herbert’s financial advisor, to Burke & Herbert’s board of directors, was delivered on and dated August 24, 2023, and the opinion from D.A. Davidson, Summit’s financial advisor, to Summit’s board of directors was delivered on and dated August 24, 2023. Changes in the operations and prospects of Burke & Herbert or Summit, general market and economic conditions and other factors which may be beyond the control of Burke & Herbert and Summit, including the ongoing effects of the COVID-19 pandemic on such market and economic conditions, and the market prices of Burke & Herbert and Summit, may have altered the value of Burke & Herbert or Summit or the prices of shares of Burke & Herbert common stock and shares of Summit common stock as of the date of this joint proxy statement/prospectus, or may alter such values and prices by the time the merger is completed. The opinions do not speak as of the date of this joint proxy statement/prospectus or as of any other date subsequent to the dates of those opinions.

Burke & Herbert and Summit are expected to incur substantial costs related to the merger and integration.

Burke & Herbert and Summit have incurred and expect to incur a number of non-recurring costs associated with the merger. These costs include legal, financial advisory, accounting, consulting and other advisory fees, severance/employee benefit-related costs, public company filing fees and other regulatory fees, financial printing and other printing costs and other related costs. Some of these costs are payable by either Burke & Herbert or Summit regardless of whether the merger is completed. See “The Merger Agreement—Expenses and Fees” beginning on page 134.

Burke & Herbert and Summit have incurred and expect to incur significant, non-recurring costs in connection with negotiating the merger agreement and closing the merger. In addition, the continuing corporation will incur integration costs following the completion of the merger as Burke & Herbert and Summit integrate their businesses, including facilities and systems consolidation costs and employment-related costs. Burke & Herbert and Summit may also incur additional costs to maintain employee morale and to retain key employees. There are a large number of processes, policies, procedures, operations, technologies and systems that may need to be integrated, including purchasing, accounting and finance, payroll, compliance, treasury management, branch operations, vendor management, risk management, lines of business, pricing and benefits. While Burke & Herbert and Summit have assumed that a certain level of costs will be incurred, there are many factors beyond their control that could affect the total amount or the timing of the integration costs. Moreover, many of the costs that will be incurred are, by their nature, difficult to estimate accurately. These integration costs may result in the continuing corporation taking charges against earnings following the completion of the merger, and the amount and timing of such charges are uncertain at present. There can be no assurances that the expected benefits and efficiencies related to the integration of the businesses will be realized to offset these transaction and integration costs over time. Anticipated future merger and integration-related pre-tax costs are currently estimated to be approximately $57 million.

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Combining Burke & Herbert and Summit may be more difficult, costly or time-consuming than expected, and Burke & Herbert and Summit may fail to realize the anticipated benefits of the merger.

This is a merger transaction combining two financial institutions of relatively similar asset size. The success of the merger will depend, in part, on the ability to realize the anticipated cost savings from combining the businesses of Burke & Herbert and Summit. To realize the anticipated benefits and cost savings from the merger, Burke & Herbert and Summit must successfully integrate and combine their businesses in a manner that permits those cost savings to be realized, without adversely affecting current revenues and future growth. If Burke & Herbert and Summit are not able to successfully achieve these objectives, the anticipated benefits of the merger may not be realized fully, or at all, or may take longer to realize than expected. In addition, the actual cost savings of the merger could be less than anticipated, and integration may result in additional and unforeseen expenses.

An inability to realize the full extent of the anticipated benefits of the merger and the other transactions contemplated by the merger agreement, as well as any delays encountered in the integration process, could have an adverse effect upon the revenues, levels of expenses and operating results of the continuing corporation following the completion of the merger, which may adversely affect the value of the common stock of the continuing corporation following the completion of the merger.

Burke & Herbert and Summit have operated and, until the completion of the merger, must continue to operate, independently. It is possible that the integration process could result in the loss of key employees, the disruption of each company’s ongoing businesses or inconsistencies in standards, controls, procedures and policies that adversely affect the companies’ ability to maintain relationships with clients, customers, depositors and employees or to achieve the anticipated benefits and cost savings of the merger. Integration efforts between the two companies may also divert management attention and resources. These integration matters could have an adverse effect on each of Burke & Herbert and Summit during this transition period and for an undetermined period after completion of the merger on the continuing corporation.

Furthermore, the board of directors of the continuing corporation will consist of former directors from each of Burke & Herbert and Summit. Combining the boards of directors of each company into a single board could require the reconciliation of differing priorities and philosophies.

The future results of the continuing corporation following the merger may suffer if the continuing corporation does not effectively manage its expanded operations, including complying with any enhanced regulatory requirements.

Following the merger, the size of the business of the continuing corporation will increase beyond the current size of either Burke & Herbert’s or Summit’s business. The continuing corporation’s future success will depend, in part, upon its ability to manage this expanded business, which may pose challenges for management, including challenges related to the management and monitoring of new operations and associated increased costs and complexity. There can be no assurances that the continuing corporation will be successful or that it will realize the expected operating efficiencies, revenue enhancement or other benefits currently anticipated from the merger.

The continuing corporation may also face increased scrutiny from governmental authorities as a result of the increased size of its business, including if the total assets of the continuing corporation grow to exceed $10 billion as of December 31 of any calendar year. Banks with $10 billion or more in total assets are, among other things: examined directly by the CFPB with respect to various federal consumer financial laws; subject to reduced dividends on any holdings of Federal Reserve Bank of Richmond common stock; subject to limits on interchange fees pursuant to the Durbin amendment to the Dodd-Frank Act; subject to certain enhanced prudential standards; no longer treated as a “small institution” for FDIC deposit insurance assessment purposes; and no longer eligible to elect to be subject to the “community bank leverage ratio.” Compliance with these additional ongoing requirements may necessitate additional personnel, the design and implementation of additional internal controls, and the incurrence of significant expenses which could have a significant adverse effect on Burke & Herbert’s financial condition or results of operations.

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The continuing corporation may be unable to retain Burke & Herbert and/or Summit personnel successfully after the merger is completed.

The success of the merger will depend in part on the continuing corporation’s ability to retain the talents and dedication of key employees currently employed by Burke & Herbert and Summit. It is possible that these employees may decide not to remain with Burke & Herbert or Summit, as applicable, while the merger is pending or with the continuing corporation after the merger is consummated. If Burke & Herbert and Summit are unable to retain key employees, including management, who are critical to the successful integration and future operations of the companies, Burke & Herbert and Summit could face disruptions in their operations, loss of existing customers, loss of key information, expertise or know-how and unanticipated additional recruitment costs. In addition, following the merger, if key employees terminate their employment, the continuing corporation’s business activities may be adversely affected, and management’s attention may be diverted from successfully hiring suitable replacements, all of which may cause the continuing corporation’s business to suffer. Burke & Herbert and Summit also may not be able to locate or retain suitable replacements for any key employees who leave either company. See “The Merger—Governance of the Continuing Corporation After the Merger” beginning on page 109.

Regulatory approvals may not be received, may take longer than expected, or may impose conditions that are not presently anticipated or that could have an adverse effect on the continuing corporation following the merger.

Before the merger and the bank merger may be completed, various approvals and consents must be obtained from the Federal Reserve Board (unless a waiver is granted), the FDIC, the VBFI, the WVDFI, and other regulatory authorities in the United States. In determining whether to grant these approvals, such regulatory authorities consider a variety of factors, including the regulatory standing of each party and the factors described under “The Merger—Regulatory Approvals” beginning on page 111. These approvals could be delayed or not obtained at all, including due to an adverse development in either party’s regulatory standing or in any other factors considered by regulators when granting such approvals; governmental, political or community group inquiries, investigations or opposition; or changes in legislation or the political environment generally.

The approvals that are granted may impose terms and conditions, limitations, obligations or costs, or place restrictions on the conduct of the continuing corporation’s business or require changes to the terms of the transactions contemplated by the merger agreement. There can be no assurance that regulators will not impose any such conditions, limitations, obligations or restrictions and that such conditions, limitations, obligations or restrictions will not have the effect of delaying the completion of any of the transactions contemplated by the merger agreement, imposing additional material costs on or materially limiting the revenues of the continuing corporation following the merger or otherwise reduce the anticipated benefits of the merger if the merger were consummated successfully within the expected timeframe. In addition, there can be no assurance that any such conditions, terms, obligations or restrictions will not result in the delay or abandonment of the merger. The completion of the merger is conditioned on the receipt of the requisite regulatory approvals and the expiration of all statutory waiting periods without the imposition of any material burdensome regulatory condition. Additionally, the completion of the merger is conditioned on the absence of certain orders, injunctions or decrees by any court or governmental entity of competent jurisdiction that would prohibit or make illegal the completion of any of the transactions contemplated by the merger agreement.

In addition, despite the parties’ commitments to using their reasonable best efforts to comply with conditions imposed by regulators, under the terms of the merger agreement, neither Burke & Herbert nor Summit, nor any of their respective subsidiaries, is permitted (without the written consent of the other party), to take any action, or commit to take any action, or agree to any condition or restriction, in connection with obtaining the required permits, consents, approvals and authorizations of governmental entities or regulatory agencies that would reasonably be expected to have a material adverse effect on the continuing corporation and its subsidiaries, taken as a whole, after giving effect to the merger and the bank merger. See “The Merger—Regulatory Approvals” beginning on page 111.

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The unaudited pro forma condensed combined financial information included in this joint proxy statement/prospectus is preliminary and the actual consideration to be issued in the merger as well as the actual financial condition and results of operations of the continuing corporation after the merger may differ materially.

The unaudited pro forma condensed combined financial information in this joint proxy statement/prospectus is presented for illustrative purposes only and is not necessarily indicative of what the continuing corporation’s actual financial condition or results of operations would have been had the merger been completed on the dates indicated. The unaudited pro forma condensed combined financial information reflects adjustments, which are based upon preliminary estimates, to record the Summit identifiable assets acquired and liabilities assumed at fair value and the resulting goodwill recognized. The merger consideration value allocation reflected in this document is preliminary, and the final allocation thereof will be based upon the value of the actual merger consideration and the fair value of the assets and liabilities of Summit as of the date of the completion of the merger. The unaudited pro forma combined financial information reflects numerous variables, expectations and assumptions available at the time it was prepared as to certain business decisions that are subject to change and does not take into account any circumstances or events occurring after the date it was prepared. Accordingly, the actual value of the merger consideration may vary significantly from the value used in preparing the unaudited pro forma condensed combined financial information in this document. Accordingly, the final acquisition accounting adjustments may differ materially from the pro forma adjustments reflected in this document and no assurances can be given that if the prospective financial information had been prepared as of the date of this joint proxy statement/prospectus, similar assumptions would be used. For more information, see “Unaudited Pro Forma Condensed Combined Financial Statements” beginning on page 139.

Certain of Burke & Herbert’s and Summit’s directors and executive officers may have interests in the merger that may differ from, or are in addition to, the interests of Burke & Herbert shareholders and Summit shareholders.

Burke & Herbert’s shareholders and Summit shareholders should be aware that some of Burke & Herbert’s and Summit’s directors and executive officers may have interests in the merger that are different from, or in addition to, those of Burke & Herbert shareholders and Summit shareholders. These interests may create potential conflicts of interest. The Burke & Herbert and Summit boards of directors were aware of these respective interests and considered these interests, among other matters, when making their decisions to approve the merger agreement, and in recommending that, in the case of the Burke & Herbert board of directors, Burke & Herbert shareholders vote to approve the merger agreement and, in the case of the Summit board of directors, Summit shareholders vote to approve the merger agreement. For a more complete description of these interests, please see “The Merger—Interests of Certain Burke & Herbert Directors and Executive Officers in the Merger” beginning on page 97 and “The Merger—Interests of Certain Summit Directors and Executive Officers in the Merger” beginning on page 98.

The merger agreement may be terminated in accordance with its terms and the merger may not be completed.

The merger agreement is subject to a number of conditions which must be fulfilled in order to complete the merger. Those conditions include: (i) approval by Burke & Herbert shareholders of the Burke & Herbert merger proposal and approval by Summit shareholders of the Summit merger proposal; (ii) authorization for listing on Nasdaq of the shares of Burke & Herbert common stock to be issued in the merger, subject to official notice of issuance; (iii) the receipt of the requisite regulatory approvals, including the approval of the Federal Reserve Board (unless a waiver is granted), the FDIC, the VBFI and the WVDFI; (iv) effectiveness of the registration statement on Form S-4 of which this joint proxy statement/prospectus forms a part; and (v) the absence of any order, injunction, decree or other legal restraint preventing the completion of the merger, the bank merger or any of the other transactions contemplated by the merger agreement or making the completion of the merger, the bank merger or any of the other transactions contemplated by the merger agreement illegal. Each party’s obligation to complete the merger is also subject to certain additional customary conditions, including (a) subject to applicable materiality standards, the accuracy of the representations and warranties of the other party, (b) the performance in all material respects by the other party of its obligations under the merger agreement, and (c) the receipt by each party of an opinion from its counsel to the effect that the merger will qualify as a reorganization within the meaning of Section 368(a) of the Code.

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These conditions to the closing may not be fulfilled in a timely manner or at all, and, accordingly, the merger may not be completed. In addition, the parties can mutually decide to terminate the merger agreement at any time, before or after the requisite shareholder approvals, or Burke & Herbert or Summit may elect to terminate the merger agreement in certain other circumstances. See “The Merger Agreement—Termination of the Merger Agreement” beginning on page 132.

Failure to complete the merger could negatively impact Burke & Herbert or Summit.

If the merger is not completed for any reason, including as a result of Burke & Herbert shareholders failing to approve the Burke & Herbert merger proposal or Summit shareholders failing to approve the Summit merger proposal, there may be various adverse consequences and Burke & Herbert and/or Summit may experience negative reactions from the financial markets and from their respective customers and employees. For example, Burke & Herbert’s or Summit’s businesses may have been impacted adversely by the failure to pursue other beneficial opportunities due to the focus of management on the merger, without realizing any of the anticipated benefits of completing the merger. Additionally, if the merger agreement is terminated, the market price of Burke & Herbert common stock or Summit common stock could decline to the extent that current market prices reflect a market assumption that the merger will be beneficial and will be completed. Burke & Herbert and/or Summit also could be subject to litigation related to any failure to complete the merger or to proceedings commenced against Burke & Herbert or Summit to perform their respective obligations under the merger agreement. If the merger agreement is terminated under certain circumstances, either Burke & Herbert or Summit may be required to pay a termination fee of $14.86 million to the other party.

Additionally, each of Burke & Herbert and Summit has incurred and will incur substantial expenses in connection with the negotiation and completion of the transactions contemplated by the merger agreement, as well as the costs and expenses of preparing, filing, printing and mailing this joint proxy statement/prospectus, and all filing and other fees paid in connection with the merger. If the merger is not completed, Burke & Herbert and Summit would have to pay these expenses without realizing the expected benefits of the merger.

In connection with the merger, Burke & Herbert will assume Summit’s outstanding debt obligations, and the continuing corporation’s level of indebtedness following the completion of the merger could adversely affect the continuing corporation’s ability to raise additional capital and to meet its obligations under its existing indebtedness.

In connection with the merger, Burke & Herbert will assume Summit’s outstanding indebtedness. Burke & Herbert’s existing debt, together with any future incurrence of additional indebtedness, and the assumption of Summit’s outstanding indebtedness, could have important consequences for the continuing corporation’s creditors and the continuing corporation’s shareholders. For example, it could:

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Burke & Herbert and Summit will be subject to business uncertainties and contractual restrictions while the merger is pending.

Uncertainty about the effect of the merger on employees and customers may have an adverse effect on Burke & Herbert and Summit. These uncertainties may impair Burke & Herbert’s or Summit’s ability to attract, retain and motivate key personnel until the merger is completed, and could cause customers and others that deal with Burke & Herbert or Summit to seek to change existing business relationships with Burke & Herbert or Summit. In addition, subject to certain exceptions, Burke & Herbert and Summit have each agreed to operate its business in the ordinary course in all material respects and to refrain from taking certain actions that may adversely affect its ability to consummate the transactions contemplated by the merger agreement on a timely basis without the consent of the other party. These restrictions may prevent Burke & Herbert and/or Summit from pursuing attractive business opportunities that may arise prior to the completion of the merger. See “The Merger Agreement—Covenants and Agreements” beginning on page 120 for a description of the restrictive covenants applicable to Burke & Herbert and Summit.

The announcement of the proposed merger could disrupt Burke & Herbert’s and Summit’s relationships with their customers, suppliers, business partners and others, as well as their operating results and businesses generally.

Whether or not the merger is ultimately consummated, as a result of uncertainty related to the proposed transactions, risks relating to the impact of the announcement of the merger on Burke & Herbert’s and Summit’s businesses include the following:

If any of the aforementioned risks were to materialize, they could lead to significant costs which may impact each party’s results of operations and financial condition.

The current rising interest rate environment may adversely impact the fair value adjustments of investments and loans acquired in the merger.

Upon the closing of the merger, the continuing corporation will need to adjust the fair value of Summit’s investment and loan portfolios. The rising interest rate environment could have the effect of increasing the magnitude of the purchase accounting marks relating to such fair value adjustments, thereby increasing initial tangible book value dilution, extending the tangible book value earn-back period, and negatively impacting the continuing corporation’s capital ratios, which may result in the continuing corporation taking steps to strengthen its capital position.

The merger agreement limits Burke & Herbert’s and Summit’s respective abilities to pursue alternatives to the merger and may discourage other companies from trying to acquire Burke & Herbert or Summit.

The merger agreement contains “no shop” covenants that restrict each of Burke & Herbert’s and Summit’s ability to, directly or indirectly, among other things, initiate, solicit, knowingly encourage or knowingly facilitate, inquiries or proposals with respect to, or, subject to certain exceptions generally related to the exercise of fiduciary duties by Burke & Herbert’s and Summit’s respective boards of directors, engage in any negotiations concerning, or provide any confidential or non-public information or data relating to, any alternative acquisition proposals. These provisions, which include a $14.86 million termination fee payable under certain circumstances, may discourage a

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potential third-party acquirer that might have an interest in acquiring all or a significant part of Burke & Herbert or Summit from considering or proposing that acquisition. For more information, see “The Merger Agreement—Agreement Not to Solicit Other Offers; Termination of the Merger Agreement; Effect of Termination; Termination Fee” and “The Merger Agreement—Meetings; Recommendation of Burke & Herbert’s and Summit’s Boards of Directors” beginning on pages 129 and 128 respectively.

The shares of Burke & Herbert common stock to be received by Summit shareholders as a result of the merger will have different rights from the shares of Summit common stock.

In the merger, Summit shareholders will become Burke & Herbert shareholders and their rights as shareholders will be governed by Virginia law and the governing documents of the continuing corporation following the merger. The rights associated with Burke & Herbert common stock are different from the rights associated with Summit common stock. See “Comparison of the Rights of Burke & Herbert shareholders and Summit Shareholders” beginning on page 155 for a discussion of the different rights associated with Burke & Herbert common stock.

Burke & Herbert shareholders and Summit shareholders will have reduced ownership and voting interest in the continuing corporation after the consummation of the merger and will exercise less influence over management.

Burke & Herbert shareholders and Summit shareholders currently have the right to vote in the election of the board of directors and on other matters affecting Burke & Herbert and Summit, respectively. When the merger is completed, each Burke & Herbert shareholder and each Summit shareholder will become a holder of common stock of the continuing corporation, with a percentage ownership of the continuing corporation that is smaller than the holder’s percentage ownership of either Burke & Herbert or Summit individually, as applicable, prior to the consummation of the merger. Based on the number of shares of Burke & Herbert common stock and Summit common stock outstanding as of the close of business on the respective record dates, and based on the number of shares of Burke & Herbert common stock expected to be issued in the merger, the former Summit shareholders, as a group, are estimated to own approximately 50% of the outstanding shares of the continuing corporation immediately after the merger and current Burke & Herbert shareholders as a group are estimated to own approximately 50% of the outstanding shares of the continuing corporation immediately after the merger. Because of this, Summit shareholders may have less influence on the management and policies of the continuing corporation than they now have on the management and policies of Summit, and Burke & Herbert shareholders may have less influence on the management and policies of the continuing corporation than they now have on the management and policies of Burke & Herbert.

Issuance of shares of Burke & Herbert common stock in connection with the merger may adversely affect the market price of Burke & Herbert common stock.

In connection with the payment of the merger consideration, Burke & Herbert expects to issue approximately 7,400,527 shares of Burke & Herbert common stock to Summit shareholders. The issuance of these new shares of Burke & Herbert common stock may result in fluctuations in the market price of Burke & Herbert common stock, including a stock price decrease.

Burke & Herbert shareholders and Summit shareholders will not have appraisal rights or dissenters’ rights in the merger.

Appraisal rights (also known as dissenters’ rights) are statutory rights that, if applicable under law, enable shareholders to dissent from an extraordinary transaction, such as a merger, and to demand that the corporation pay the fair value for their shares as determined by a court in a judicial proceeding instead of receiving the consideration offered to shareholders in connection with the extraordinary transaction. Burke & Herbert shareholders and Summit shareholders are not entitled under applicable law to appraisal rights in connection with the merger.

Shareholder litigation could prevent or delay the completion of the merger or otherwise negatively impact the business and operations of Burke & Herbert and Summit.

Shareholders of Burke & Herbert and/or of Summit may file lawsuits against Burke & Herbert, Summit and/or the directors and officers of either company in connection with the merger. One of the conditions to the closing is

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that no order, injunction or decree issued by any court or governmental entity of competent jurisdiction or other legal restraint preventing the consummation of the merger, the bank merger or any of the other transactions contemplated by the merger agreement be in effect. If any plaintiff were successful in obtaining an injunction prohibiting Burke & Herbert or Summit defendants from completing the merger, the bank merger or any of the other transactions contemplated by the merger agreement, then such injunction may delay or prevent the effectiveness of the merger and could result in significant costs to Burke & Herbert and/or Summit, including any cost associated with the indemnification of directors and officers of each company. Burke & Herbert and Summit may incur costs in connection with the defense or settlement of any shareholder lawsuits filed in connection with the merger. Such litigation could have an adverse effect on the financial condition and results of operations of Burke & Herbert and Summit and could prevent or delay the completion of the merger.

Risks Relating to Burke & Herbert’s Business

You should read and consider risk factors specific to Burke & Herbert’s business that will also affect the continuing corporation after the mergers. These risks are described in the “Risk Factors” section of Burke & Herbert’s Form 10 registration statement, as amended and declared effective by the SEC on April 21, 2023, and in any updates to those risk factors set forth in Burke & Herbert’s Quarterly Reports on Form 10-Q and in other documents attached as annexes to this joint proxy statement/prospectus. Please see the section entitled “Where You Can Find More Information” beginning on page 176 of this joint proxy statement/prospectus for the location of information that is attached as annexes to this joint proxy statement/prospectus.

Risks Relating to Summit’s Business

You should read and consider risk factors specific to Summit’s business that will also affect the continuing corporation after the merger. These risks are described in the “Risk Factors” section of Summit’s Annual Report on Form 10-K for the year ended December 31, 2022, and in any updates to those risk factors set forth in Summit’s Quarterly Reports on Form 10-Q and in other documents incorporated by reference into this joint proxy statement/prospectus. Please see the section entitled “Where You Can Find More Information” beginning on page 176 of this joint proxy statement/prospectus for the location of information incorporated by reference into this joint proxy statement/prospectus.

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THE BURKE & HERBERT SPECIAL MEETING

This section contains information for Burke & Herbert shareholders about the special meeting that Burke & Herbert has called to allow Burke & Herbert shareholders to consider and vote on the Burke & Herbert merger proposal and the Burke & Herbert adjournment proposal. This joint proxy statement/prospectus is accompanied by a notice of the Burke & Herbert special meeting, and a form of proxy card that the Burke & Herbert board of directors is soliciting for use by Burke & Herbert shareholders at the special meeting and at any adjournments or postponements of the special meeting.

Date, Time and Place of the Meeting

The Burke & Herbert special meeting will be held virtually via the internet on December 6, 2023 at 8:00 a.m., Eastern Time. The Burke & Herbert special meeting will be held in a virtual-only meeting format conducted via live webcast. Shareholders may participate in the virtual meeting by accessing https://web.lumiagm.com/261284453.

Matters to Be Considered

At the Burke & Herbert special meeting, Burke & Herbert shareholders will be asked to consider and vote upon the following proposals:

Recommendation of Burke & Herbert’s Board of Directors

The Burke & Herbert board of directors recommends that you vote “FOR” the Burke & Herbert merger proposal and “FOR” the Burke & Herbert adjournment proposal. See “The Merger—Burke & Herbert’s Reasons for the Merger; Recommendation of Burke & Herbert’s Board of Directors” beginning on page 62 for a more detailed discussion of the Burke & Herbert board of directors’ recommendation.

Record Date and Quorum

The Burke & Herbert board of directors has fixed the close of business on October 12, 2023 as the record date for the determination of Burke & Herbert shareholders entitled to notice of and to vote at the Burke & Herbert special meeting. As of the Burke & Herbert record date, there were 7,428,710 shares of Burke & Herbert common stock outstanding.

Holders of a majority of the outstanding shares of Burke & Herbert common stock entitled to vote at the Burke & Herbert special meeting must be present, either in attendance virtually via the Burke & Herbert special meeting website or by proxy, to constitute a quorum at the Burke & Herbert special meeting. If you fail to submit a proxy prior to the special meeting or to vote at the Burke & Herbert special meeting via the Burke & Herbert special meeting website, your shares of Burke & Herbert common stock will not be counted towards a quorum. Abstentions will be included in determining the number of shares present at the meeting for the purpose of determining the presence of a quorum, but not a broker non-vote or other failure to vote.

Under the Burke & Herbert bylaws, if a quorum is not present at the Burke & Herbert special meeting, the holders of a majority of the shares of Burke & Herbert common stock entitled to vote who are present (including virtually via the Burke & Herbert special meeting website) or by proxy at the Burke & Herbert special meeting may adjourn the Burke & Herbert special meeting.

At the Burke & Herbert special meeting, each share of Burke & Herbert common stock is entitled to one vote on all matters properly submitted to Burke & Herbert shareholders.

As of the close of business on the record date, Burke & Herbert’s directors and executive officers and their affiliates were entitled to vote an aggregate of 1,094,460 shares of Burke & Herbert common stock at the special

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meeting, which represents approximately 14.7% of the issued and outstanding shares of Burke & Herbert common stock entitled to vote at the special meeting.

Each director of Burke & Herbert, solely in such director’s capacity as a shareholder of Burke & Herbert, has entered into an affiliate agreement with Summit requiring them to vote all shares of Burke & Herbert common stock that such director beneficially owns and has the sole right to vote or transfer in favor of the Burke & Herbert merger proposal. As of the record date, these directors held 131,520 shares of Burke & Herbert common stock subject to such agreements, which represented approximately 1.8% of the outstanding shares of Burke & Herbert common stock.

Broker Non-Votes

A broker non-vote occurs when a bank, broker, trustee or other nominee is not permitted to vote on a “non-routine” matter without instructions from the beneficial owner of the shares and the beneficial owner fails to provide the bank, broker, trustee or other nominee with such instructions. Broker non-votes only count toward a quorum if at least one proposal is presented with respect to which the bank, broker, trustee or other nominee has discretionary authority. It is expected that all proposals to be voted on at the Burke & Herbert special meeting will be “non-routine” matters, and, as such, broker non-votes, if any, will not be counted as present and entitled to vote for purposes of determining a quorum at the Burke & Herbert special meeting. If your bank, broker, trustee or other nominee holds your shares of Burke & Herbert common stock in “street name,” such entity will vote your shares of Burke & Herbert common stock only if you provide instructions on how to vote by complying with the instructions provided to you by your bank, broker, trustee or other nominee with this joint proxy statement/prospectus.

Vote Required; Treatment of Abstentions and Failure to Vote

Burke & Herbert merger proposal:

Vote required: Approval of the Burke & Herbert merger proposal requires the affirmative vote of a majority of the votes entitled to be cast by the holders of outstanding shares of Burke & Herbert common stock at the Burke & Herbert special meeting. Approval of the Burke & Herbert merger proposal is a condition to the completion of the merger.

Effect of abstentions and failure to vote: If you are present at the Burke & Herbert special meeting and abstain from voting, or respond by proxy with an “ABSTAIN,” it will have the same effect as a vote “AGAINST” such proposal. If you are not present at the Burke & Herbert special meeting and do not respond by proxy or do not provide your bank, broker, trustee or other nominee with instructions, as applicable, it will have the same effect as a vote “AGAINST” such proposal.

Burke & Herbert adjournment proposal:

Vote required: If a quorum is present at the Burke & Herbert special meeting, approval of the Burke & Herbert adjournment proposal requires the affirmative vote of a majority of the votes cast affirmatively or negatively by the Burke & Herbert shareholders at the Burke & Herbert special meeting. In the absence of a quorum at the Burke & Herbert special meeting, approval of the Burke & Herbert adjournment proposal requires the affirmative vote of a majority of the shares of Burke & Herbert common stock present at the Burke & Herbert special meeting and entitled to vote on the Burke & Herbert adjournment proposal.

Effect of abstentions and failure to vote: If a quorum is present at the Burke & Herbert special meeting, if you are present at the Burke & Herbert special meeting and abstain from voting, or respond by proxy with an “ABSTAIN,” it will have no effect on the outcome of such proposal. In the absence of a quorum at the Burke & Herbert special meeting, if you are present at the Burke & Herbert special meeting and abstain from voting, or respond by proxy with an “ABSTAIN,” it will have the same effect as a vote “AGAINST” the proposal. Whether or not a quorum is present at the Burke & Herbert special meeting, if you are not present at the Burke & Herbert special meeting and do not respond by proxy or do not provide your bank, broker, trustee or other nominee with instructions, as applicable, it will have no effect on the outcome of such proposal.

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Attending the Virtual Special Meeting

The Burke & Herbert special meeting may be accessed via the Burke & Herbert special meeting website, where Burke & Herbert shareholders will be able to listen to the Burke & Herbert special meeting, submit questions and vote online. You are entitled to attend the Burke & Herbert special meeting via the Burke & Herbert special meeting website only if you were a shareholder of record at the close of business on the record date (a “record holder”) or you held your Burke & Herbert shares beneficially in the name of a bank, broker, trustee or other nominee as of the record date (a “beneficial owner”), or you hold a valid proxy for the Burke & Herbert special meeting.

If you are a record holder, you will be able to attend the Burke & Herbert special meeting online, ask questions and vote during the meeting by visiting https://web.lumiagm.com/261284453 and following the instructions. Please have your control number, which can be found on your notice, proxy card or voting instruction form, to access the meeting. The password for the meeting, if requested, is burke2023.

If you hold your shares through an intermediary, such as a bank or broker, you must register in advance using the instructions provided in accompanying proxy materials. If you do not have your control number, you may attend the special meeting as a guest (non-shareholder), but you will not have the ability to vote your shares or submit questions during the special meeting. See “—Shares Held in Street Name” below for further information.

If you are a beneficial owner of Burke & Herbert common stock, in order to participate in the Burke & Herbert special meeting, you must first obtain a legal proxy from your broker, bank or other nominee reflecting the number of shares of Burke & Herbert common stock you held as of the record date, your name and email address. You then must submit a request for registration to Equiniti: (1) by email to proxy@equiniti.com; (2) by fax to (718) 765-8730, or (3) by mail to Equiniti Trust Company, LLC, Attn: Proxy Tabulation Department, 6201 15th Avenue, Brooklyn, NY 11219. Requests for registration must be labeled as “Legal Proxy” and be received by Equiniti no later than 5:00 p.m.. Eastern Time on November 20, 2023. Please review this information prior to the Burke & Herbert special meeting to ensure you have access. See “—Shares Held in Street Name” below for further information.

Shareholders will have substantially the same opportunities to participate in the virtual Burke & Herbert special meeting as they would have at a physical, in-person meeting. Shareholders as of the record date will be able to attend, vote, and submit questions during a portion of the meeting via the online platform. To ensure the Burke & Herbert special meeting is conducted in a manner that is fair to all shareholders, Burke & Herbert may exercise discretion in determining the order in which questions are answered and the amount of time devoted to any one question. Burke & Herbert reserves the right to edit or reject questions Burke & Herbert deems inappropriate or not relevant to the Burke & Herbert special meeting’s limited purpose.

Proxies

A holder of Burke & Herbert common stock may vote by proxy or at the Burke & Herbert special meeting via the Burke & Herbert special meeting website. If you hold your shares of Burke & Herbert common stock in your name as a record holder, to submit a proxy, you, as a holder of Burke & Herbert common stock, may use one of the following methods:

Burke & Herbert requests that Burke & Herbert shareholders vote by telephone, over the internet or by completing and signing the accompanying proxy card and returning it to Burke & Herbert as soon as possible in the enclosed postage-paid envelope. When the accompanying proxy card is returned properly executed, the shares of Burke & Herbert common stock represented by it will be voted at the Burke & Herbert special meeting in

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accordance with the instructions contained on the proxy card. If you make no specification on your proxy card as to how you want your shares voted before signing and returning it, your proxy will be voted “FOR” the Burke & Herbert merger proposal and “FOR” the Burke & Herbert adjournment proposal.

If you are a beneficial owner, the holder should check the voting form used by your bank, broker, trustee or other nominee to determine whether the holder may vote by telephone or the internet.

Every vote is important. Accordingly, you should sign, date and return the enclosed proxy card, or vote via the internet or by telephone, whether or not you plan to attend the Burke & Herbert special meeting virtually via the Burke & Herbert special meeting website. Sending in your proxy card or voting by telephone or on the internet will not prevent you from voting your shares personally via the Burke & Herbert special meeting website at the meeting because you may revoke your proxy at any time before it is voted.

Shares Held in Street Name

If your shares are held in “street name” through a bank, broker, trustee or other nominee, you must instruct the bank, broker, trustee or other nominee on how to vote your shares. Your bank, broker, trustee or other nominee will vote your shares only if you provide specific instructions on how to vote by following the instructions provided to you by your bank, broker, trustee or other nominee.

Further, banks, brokers, trustees or other nominees who hold shares of Burke & Herbert common stock on behalf of their customers may not give a proxy to Burke & Herbert to vote those shares with respect to any of the proposals without specific instructions from their customers, as banks, brokers, trustees and other nominees do not have discretionary voting power on the proposals that will be voted upon at the Burke & Herbert special meeting, including the Burke & Herbert merger proposal and the Burke & Herbert adjournment proposal.

Revocability of Proxies

If you directly hold shares of Burke & Herbert common stock in your name as a record holder, you can change your vote at any time before your proxy is voted at the meeting. You can do this by:

If your shares are held in street name, you should follow your bank’s, broker’s, trustee’s or other nominee’s instructions regarding the revocation of proxies.

Attendance virtually at the Burke & Herbert special meeting will not in and of itself constitute revocation of a proxy. A revocation or later-dated proxy received by Burke & Herbert after the vote will not affect the vote. Written notices of revocation and other communications regarding the revocation of your proxy should be addressed to: Burke & Herbert Financial Services Corp., 100 S. Fairfax Street, Alexandria, VA 22314, Attention: Corporate Secretary. If the Burke & Herbert virtual special meeting is postponed or adjourned, it will not affect the ability of Burke & Herbert shareholders of record as of the record date to exercise their voting rights or to revoke any previously granted proxy using the methods described above.

Delivery of Proxy Materials

As permitted by applicable law, only one copy of this joint proxy statement/prospectus is being delivered to Burke & Herbert shareholders residing at the same address, unless such Burke & Herbert shareholders have notified Burke & Herbert of their desire to receive multiple copies of the joint proxy statement/prospectus.

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Burke & Herbert will promptly deliver, upon oral or written request, a separate copy of the joint proxy statement/prospectus to any Burke & Herbert shareholder residing at an address to which only one copy of such document was mailed. Requests for additional copies should be directed to Burke & Herbert’s proxy solicitor, Regan & Associates, Inc. at the following address: 505 Eighth Avenue, Suite 800, New York, New York 10018, or by telephone at (212) 587-3005.

Solicitation of Proxies

Burke & Herbert and Summit will share equally the expenses incurred in connection with the printing and mailing of this joint proxy statement/prospectus. To assist in the solicitation of proxies, Burke & Herbert has retained Regan & Associates, Inc. as its proxy solicitor, and will pay them a fee of $18,500, which includes expenses for these services. Burke & Herbert and its proxy solicitor may also request banks, brokers, trustees and other intermediaries holding shares of Burke & Herbert common stock beneficially owned by others to send this document to, and obtain proxies from, the beneficial owners and may reimburse such record holders for their reasonable out-of-pocket expenses in so doing. Solicitation of proxies by mail may be supplemented by telephone and other electronic means, advertisements and personal solicitation by the directors, officers or employees of Burke & Herbert. No additional compensation will be paid to Burke & Herbert’s directors, officers or employees for solicitation.

Other Matters to Come Before the Burke & Herbert Special Meeting

Burke & Herbert management knows of no other business to be presented at the Burke & Herbert special meeting, but if any other matters are properly presented to the meeting or any adjournments thereof, the persons named in the proxies will vote upon them in accordance with the Burke & Herbert board of directors’ recommendations.

Assistance

If you need assistance in completing your proxy card, have questions regarding Burke & Herbert’s special meeting or would like additional copies of this joint proxy statement/prospectus, please contact Burke & Herbert Financial Services Corp., Attn: Investor Relations, 100 S. Fairfax Street, Alexandria, VA 22314, telephone (703) 666-3555, or Burke & Herbert’s proxy solicitor, Regan & Associates, Inc. at the following address: 505 Eighth Avenue, Suite 800, New York, New York 10018, or by telephone at (212) 587-3005.

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BURKE & HERBERT PROPOSALS

Proposal 1: Burke & Herbert Merger Proposal

Pursuant to the merger agreement, Burke & Herbert is asking Burke & Herbert shareholders to approve the merger agreement. Burke & Herbert shareholders should read this joint proxy statement/prospectus carefully and in its entirety, including the annexes, for more detailed information concerning the merger agreement and the transactions contemplated thereby. A copy of the merger agreement is attached to this joint proxy statement/prospectus as Annex A.

After careful consideration, the Burke & Herbert board of directors, by a unanimous vote of all directors, approved the merger agreement and declared the merger agreement and the transactions contemplated thereby, including the merger and bank merger, to be advisable and in the best interest of Burke & Herbert and Burke & Herbert shareholders. See “The Merger—Burke & Herbert’s Reasons for the Merger; Recommendation of Burke & Herbert’s Board of Directors” beginning on page 62 for a more detailed discussion of the Burke & Herbert board of directors’ recommendation.

The approval of the Burke & Herbert merger proposal by Burke & Herbert shareholders is a condition to the completion of the merger.

The Burke & Herbert board of directors unanimously recommends a vote “FOR” the Burke & Herbert merger proposal.

Proposal 2: Burke & Herbert Adjournment Proposal

The Burke & Herbert special meeting may be adjourned to another time or place, if necessary or appropriate, to solicit additional proxies if there are insufficient votes at the time of the Burke & Herbert special meeting to approve the Burke & Herbert merger proposal or to ensure that any supplement or amendment to this joint proxy statement/prospectus is timely provided to Burke & Herbert shareholders. If, at the Burke & Herbert special meeting, the number of shares of Burke & Herbert common stock present or represented and voting in favor of Burke & Herbert merger proposal is insufficient to approve the Burke & Herbert merger proposal, Burke & Herbert intends to move to adjourn the Burke & Herbert special meeting in order to enable the Burke & Herbert board of directors to solicit additional proxies for approval of the Burke & Herbert merger proposal. In that event, Burke & Herbert will ask Burke & Herbert shareholders to vote upon the Burke & Herbert adjournment proposal, but not the Burke & Herbert merger.

In this proposal, Burke & Herbert is asking Burke & Herbert shareholders to authorize the holder of any proxy solicited by the Burke & Herbert board of directors, on a discretionary basis (i) if there are not sufficient votes at the time of the Burke & Herbert special meeting to approve the Burke & Herbert merger proposal or (ii) if necessary or appropriate to ensure that any supplement or amendment to this joint proxy statement/prospectus is timely provided to Burke & Herbert shareholders, to vote in favor of adjourning the Burke & Herbert special meeting to another time and place for the purpose of soliciting additional proxies, including the solicitation of proxies from Burke & Herbert shareholders who have previously voted. Pursuant to the Burke & Herbert bylaws, the Burke & Herbert special meeting may be adjourned without new notice being given.

The approval of the Burke & Herbert adjournment proposal by Burke & Herbert shareholders is not a condition to the completion of the merger.

The Burke & Herbert board of directors unanimously recommends a vote “FOR” the Burke & Herbert adjournment proposal.

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THE SUMMIT SPECIAL MEETING

This section contains information for Summit shareholders about the special meeting that Summit has called to allow Summit shareholders to consider and vote on the Summit merger proposal, the Summit compensation proposal and the Summit adjournment proposal. This joint proxy statement/prospectus is accompanied by a notice of the Summit special meeting and a form of proxy card that the Summit board of directors is soliciting for use by Summit shareholders at the special meeting and at any adjournments or postponements of the special meeting.

Date, Time and Place of the Meeting

The Summit special meeting will be held at Summit’s corporate office located at 300 North Main Street, Moorefield, WV 26836 on December 6, 2023 at 1:00 p.m., Eastern Time.

Matters to Be Considered

At the Summit special meeting, Summit shareholders will be asked to consider and vote upon the following proposals:

Recommendation of Summit’s Board of Directors

The Summit board of directors recommends that you vote “FOR” the Summit merger proposal, “FOR” the Summit compensation proposal and “FOR” the Summit adjournment proposal. See “The Merger—Summit’s Reasons for the Merger; Recommendation of Summit’s Board of Directors” beginning on page 76 for a more detailed discussion of the Summit board of directors’ recommendation.

Record Date and Quorum

The Summit board of directors has fixed the close of business on October 12, 2023 as the record date for the determination of Summit shareholders entitled to notice of and to vote at the Summit special meeting. As of the Summit record date, there were 14,674,852 shares of Summit common stock outstanding.

Holders of a majority of the outstanding shares of Summit common stock entitled to vote at the Summit special meeting must be present, either in attendance at the Summit special meeting or by proxy, to constitute a quorum at the Summit special meeting. If you fail to submit a proxy prior to the special meeting or to vote at the Summit special meeting, your shares of Summit common stock will not be counted towards a quorum. Abstentions will be included in determining the number of shares present at the meeting for the purpose of determining the presence of a quorum, but not a broker non-vote or other failure to vote.

At the Summit special meeting, each share of Summit common stock is entitled to one vote on all matters properly submitted to Summit shareholders. Shares of Summit series 2021 preferred stock are not entitled to vote at the Summit special meeting.

As of the close of business on the record date, Summit directors and executive officers and their affiliates were entitled to vote an aggregate of 1,629,557 shares of Summit common stock at the special meeting, which represents approximately 11.1% of the issued and outstanding shares of Summit common stock entitled to vote at the special meeting.

Each director of Summit, solely in such director’s capacity as a shareholder of Summit, has entered into an affiliate agreement with Burke & Herbert requiring each of them to vote all shares of Summit common stock that such director beneficially owns and has the sole right to vote or transfer in favor of the Summit merger proposal. As of the record date, these directors held 614,244 shares of Summit common stock subject to such agreements, which

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represented approximately 4.2% of the outstanding shares of Summit common stock. Additionally, former Summit director John W. Crites, II, has entered into an affiliate agreement with Burke & Herbert requiring him to vote 132 shares of Summit common stock, which are all of the shares that he beneficially owns and has the sole right to vote or transfer, in favor of the Summit merger proposal.

Broker Non-Votes

A broker non-vote occurs when a bank, broker, trustee or other nominee is not permitted to vote on a “non-routine” matter without instructions from the beneficial owner of the shares and the beneficial owner fails to provide the bank, broker, trustee or other nominee with such instructions. Broker non-votes only count toward a quorum if at least one proposal is presented with respect to which the bank, broker, trustee or other nominee has discretionary authority. It is expected that all proposals to be voted on at the Summit special meeting will be “non-routine” matters, and, as such, broker non-votes, if any, will not be counted as present and entitled to vote for purposes of determining a quorum at the Summit special meeting. If your bank, broker, trustee or other nominee holds your shares of Summit common stock in “street name,” such entity will vote your shares of Summit common stock only if you provide instructions on how to vote by complying with the instructions provided to you by your bank, broker, trustee or other nominee with this joint proxy statement/prospectus.

Vote Required; Treatment of Abstentions and Failure to Vote

Summit merger proposal:

Vote required: The Summit merger proposal will be approved if a majority of all of the votes entitled to be cast at the special meeting are voted in favor of such proposal. If a Summit shareholder present at the Summit special meeting abstains from voting, or responds by proxy with an “ABSTAIN,” it will have the same effect as a vote “AGAINST” such proposal. If a Summit shareholder is not present at the Summit special meeting and does not respond by proxy or does not provide his, her or its bank, broker, trustee or other nominee with instructions, as applicable and as may be required, it will have the same effect as a vote “AGAINST” such proposal.

Effect of abstentions and failure to vote: If you are present at the Summit special meeting and abstain from voting, or respond by proxy with an “ABSTAIN,” it will have the same effect as a vote “AGAINST” the Summit merger proposal. If you are not present at the Summit special meeting and do not respond by proxy or do not provide your bank, broker, trustee or other nominee with instructions, as applicable and as may be required, it will have the same effect as a vote “AGAINST” the merger proposal.

Summit compensation proposal:

Vote required: Approval of the Summit compensation proposal requires the affirmative vote of a majority of the votes cast affirmatively or negatively by the holders of outstanding shares of Summit common stock in attendance at the Summit special meeting or represented by proxy at the Summit special meeting. Approval of the Summit compensation proposal is not a condition to the completion of the merger. Because this proposal is advisory in nature only, a vote for or against approval will not be binding on either Summit or Burke & Herbert, regardless of whether the other proposals are approved.

Effect of abstentions and failure to vote: If you are present at the Summit special meeting and abstain from voting, or respond by proxy with an “ABSTAIN,” it will have no effect on the outcome of such proposal. If you are not present at the Summit special meeting and do not respond by proxy or do not provide your bank, broker, trustee or other nominee with instructions, as applicable and as may be required, it will have no effect on the vote count for such proposal.

Summit adjournment proposal:

Vote required: If a quorum is present at the Summit special meeting, approval of the Summit adjournment proposal requires the affirmative vote of a majority of the votes cast affirmatively or negatively by the holders of Summit common stock at the Summit special meeting. In the absence of a quorum at the Summit special meeting,

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approval of the Summit adjournment proposal requires the affirmative vote of a majority of the shares of Summit common stock present at the Summit special meeting and entitled to vote on the Summit adjournment proposal.

Effect of abstentions and failure to vote: If a quorum is present at the Summit special meeting, if you are present at the Summit special meeting and abstain from voting, or respond by proxy with an “ABSTAIN,” it will have no effect on the outcome of such proposal. In the absence of a quorum at the Summit special meeting, if you are present at the Summit special meeting and abstain from voting, or respond by proxy with an “ABSTAIN,” it will have the same effect as a vote “AGAINST” the proposal. Whether or not a quorum is present at the Summit special meeting, if you are not present at the Summit special meeting and do not respond by proxy or do not provide your bank, broker, trustee or other nominee with instructions, as applicable, it will have no effect on the outcome of such proposal.

Attending the Summit Special Meeting

All holders of Summit common stock, including holders of record and shareholders who beneficially hold their stock through banks, brokers, nominees or any other holder of record, are invited to attend the special meeting. Shareholders of record on the record date can vote in person at the special meeting. If you beneficially hold your shares in “street name,” you must obtain a written proxy executed in your favor from the record holder of your shares, such as a broker, bank or other nominee, to be able to vote in person at the special meeting. If you plan to attend the special meeting, you must either hold your shares in your own name or have a letter from the record holder of your shares confirming your ownership.

Proxies

A holder of Summit common stock may vote by proxy or at the Summit special meeting. If you hold your shares of Summit common stock in your name as a record holder, to submit a proxy, you, as a holder of Summit common stock, may use one of the following methods:

Summit requests that Summit shareholders vote by telephone, over the internet or by completing and signing the accompanying proxy card and returning it to Summit as soon as possible in the enclosed postage-paid envelope. When the accompanying proxy card is returned properly executed, the shares of Summit common stock represented by it will be voted at the Summit special meeting in accordance with the instructions contained on the proxy card. If you make no specification on your proxy card as to how you want your shares voted before signing and returning it, your proxy will be voted “FOR” the Summit merger proposal, “FOR” the Summit compensation proposal and “FOR” the Summit adjournment proposal.

If you are a beneficial owner, the holder should check the voting form used by your bank, broker, trustee or other nominee to determine whether the holder may vote by telephone or the internet.

Every vote is important. Accordingly, you should sign, date and return the enclosed proxy card, or vote via the internet or by telephone, whether or not you plan to attend the Summit special meeting. Sending in your proxy card or voting by telephone or on the internet will not prevent you from voting your shares personally at the Summit special meeting because you may revoke your proxy at any time before it is voted.

Shares Held in Street Name

If your shares are held in “street name” through a bank, broker, trustee or other nominee, you must instruct the bank, broker, trustee or other nominee on how to vote your shares. Your bank, broker, trustee or other nominee will

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vote your shares only if you provide specific instructions on how to vote by following the instructions provided to you by your bank, broker, trustee or other nominee.

Further, banks, brokers, trustees or other nominees who hold shares of Summit common stock on behalf of their customers may not give a proxy to Summit to vote those shares with respect to any of the proposals without specific instructions from their customers, as banks, brokers, trustees and other nominees do not have discretionary voting power on the proposals that will be voted upon at the Summit special meeting, including the Summit merger proposal, the Summit compensation proposal and the Summit adjournment proposal.

Revocability of Proxies

If you directly hold shares of Summit common stock in your name as a record holder, you can change your vote at any time before your proxy is voted at your meeting. You can do this by:

If your shares are held in street name, you should follow your bank’s, broker’s, trustee’s or other nominee’s instructions regarding the revocation of proxies.

Attendance at the Summit special meeting will not in and of itself constitute revocation of a proxy. A revocation or later-dated proxy received by Summit after the vote will not affect the vote. Written notices of revocation and other communications regarding the revocation of your proxy should be addressed to Summit Financial Group, Inc., P.O. Box 179, Moorefield, WV 26836, Attention: Teresa D. Ely, Director of Shareholder Relations. If the Summit virtual special meeting is postponed or adjourned, it will not affect the ability of Summit shareholders of record as of the record date to exercise their voting rights or to revoke any previously granted proxy using the methods described above.

Participants in the ESOP

Pursuant to the ESOP, the trustee of the ESOP votes the shares of Summit common stock allocated to a participant in accordance with the participant’s instructions if instructions have been timely received. If you participate in the ESOP, you will receive a voting instruction card that reflects all shares of Summit common stock you may direct the trustee to vote on your behalf under the ESOP. The trustee is permitted to vote the shares of Summit common stock allocated to a participant’s account for which no instructions have been timely received, in the exercise of the trustee’s fiduciary discretion.

Delivery of Proxy Materials

As permitted by applicable law, only one copy of this joint proxy statement/prospectus is being delivered to Summit shareholders residing at the same address, unless such Summit shareholders have notified Summit of their desire to receive multiple copies of the joint proxy statement/prospectus.

Summit will promptly deliver, upon oral or written request, a separate copy of the joint proxy statement/prospectus to any Summit shareholder residing at an address to which only one copy of such document was mailed. Requests for additional copies should be directed to Summit’s Director of Shareholder Relations, Teresa D. Ely, at the following address: P.O. Box 179, Moorefield, WV 26836, or by telephone at (304) 530-0526.

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Solicitation of Proxies

Burke & Herbert and Summit will share equally the expenses incurred in connection with the printing and mailing of this joint proxy statement/prospectus. Summit and its Director of Shareholder Relations, Teresa D. Ely, may also request banks, brokers, trustees and other intermediaries holding shares of Summit common stock beneficially owned by others to send this document to, and obtain proxies from, the beneficial owners and may reimburse such record holders for their reasonable out-of-pocket expenses in so doing. Solicitation of proxies by mail may be supplemented by telephone and other electronic means, advertisements and personal solicitation by the directors, officers or employees of Summit. No additional compensation will be paid to Summit’s directors, officers or employees for solicitation.

You should not send in any Summit stock certificates with your proxy card (or, if you are a beneficial owner, your voting instruction card). The exchange agent will mail a transmittal letter with instructions for the surrender of stock certificates to Summit shareholders as soon as practicable after completion of the merger.

Other Matters to Come Before the Summit Special Meeting

Summit management knows of no other business to be presented at the Summit special meeting, but if any other matters are properly presented to the meeting or any adjournments thereof, the persons named in the proxies will vote upon them in accordance with the Summit board of directors’ recommendations.

Assistance

If you need assistance in completing your proxy card, have questions regarding Summit’s special meeting or would like additional copies of this joint proxy statement/prospectus, please contact Teresa D. Ely, Director of Shareholder Relations at P.O. Box 179, Moorefield, WV 26836, or by telephone at (304) 530-0526.

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SUMMIT PROPOSALS

Proposal 1: Summit Merger Proposal

Pursuant to the merger agreement, Summit is asking Summit shareholders to approve the merger agreement. Summit shareholders should read this joint proxy statement/prospectus carefully and in its entirety, including the annexes, for more detailed information concerning the merger agreement and the transactions contemplated thereby. A copy of the merger agreement is attached to this joint proxy statement/prospectus as Annex A.

After careful consideration, the Summit board of directors, by a unanimous vote of all directors, approved and adopted the merger agreement and declared the merger agreement and the transactions contemplated thereby, including the merger and bank merger, to be advisable and in the best interest of Summit and Summit shareholders. See “The Merger—Summit’s Reasons for the Merger; Recommendation of Summit’s Board of Directors” beginning on page 76 for a more detailed discussion of the Summit board of directors’ recommendation.

The approval of the Summit merger proposal by Summit shareholders is a condition to the completion of the merger.

The Summit board of directors unanimously recommends a vote “FOR” the Summit merger proposal.

Proposal 2: Summit Compensation Proposal

Pursuant to Section 14A of the Exchange Act and Rule 14a-21(c) thereunder, Summit is seeking a non-binding, advisory shareholder approval of the compensation of Summit’s named executive officers that is based on or otherwise relates to the merger as disclosed in the section entitled “The Merger—Interests of Certain Summit Directors and Executive Officers in the Merger” beginning on page 98. The proposal gives Summit shareholders the opportunity to express their views on the merger-related compensation of Summit’s named executive officers.

Accordingly, Summit is asking Summit shareholders to vote “FOR” the adoption of the following resolution, on a non-binding advisory basis:

“RESOLVED, that the compensation that will or may be paid or become payable to the Summit named executive officers, in connection with the merger, and the agreements or understandings pursuant to which such compensation will or may be paid or become payable, in each case as disclosed pursuant to Item 402(t) of Regulation S-K in “Interests of Certain Summit Directors and Executive Officers in the Merger—Potential Payments and Benefits to Summit’s Named Executive Officers in Connection with the Merger,” are hereby APPROVED.”

The advisory vote on the Summit compensation proposal is a vote separate and apart from the votes on the Summit merger proposal and the Summit adjournment proposal. Accordingly, if you are a holder of Summit common stock, you may vote to approve the Summit merger proposal and/or the Summit adjournment proposal and vote not to approve the Summit compensation proposal, and vice versa. The approval of the Summit compensation proposal by Summit shareholders is not a condition to the completion of the merger. If the merger is completed, the merger-related compensation will be paid to Summit’s named executive officers to the extent payable in accordance with the terms of the compensation agreements and arrangements even if Summit shareholders fail to approve the advisory vote regarding merger-related compensation.

The Summit board of directors unanimously recommends a vote “FOR” the advisory Summit compensation proposal.

Proposal 3: Summit Adjournment Proposal

The Summit special meeting may be adjourned to another time or place, if necessary or appropriate, to solicit additional proxies if there are insufficient votes at the time of the Summit special meeting to approve the Summit merger proposal or to ensure that any supplement or amendment to this joint proxy statement/prospectus is timely provided to Summit shareholders.

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If, at the Summit special meeting, the number of shares of Summit common stock present or represented and voting in favor of the Summit merger proposal is insufficient to approve the Summit merger proposal, Summit intends to move to adjourn the Summit special meeting in order to enable the Summit board of directors to solicit additional proxies for approval of the Summit merger proposal. In that event, Summit will ask Summit shareholders to vote upon the Summit adjournment proposal, but not the Summit merger proposal or the Summit compensation proposal.

In this proposal, Summit is asking Summit shareholders to authorize the holder of any proxy solicited by the Summit board of directors on a discretionary basis (i) if there are not sufficient votes at the time of the Summit special meeting to approve the Summit merger proposal or (ii) if necessary or appropriate to ensure that any supplement or amendment to this joint proxy statement/prospectus is timely provided to Summit shareholders, to vote in favor of adjourning the Summit special meeting to another time and place for the purpose of soliciting additional proxies, including the solicitation of proxies from Summit shareholders who have previously voted. Pursuant to the Summit bylaws, the Summit special meeting may be adjourned without new notice being given, unless the board of directors fixes a new record date for the adjourned meeting, which it may do if the adjourned date is not more than 120 days after the date fixed for the original meeting.

The approval of the Summit adjournment proposal by Summit shareholders is not a condition to the completion of the merger.

The Summit board of directors unanimously recommends a vote “FOR” the Summit adjournment proposal.

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INFORMATION ABOUT THE COMPANIES

Burke & Herbert

Burke & Herbert was organized as a Virginia corporation in 2022 to serve as the holding company for B&H Bank. Burke & Herbert commenced operations as a bank holding company on October 1, 2022 following a reorganization transaction in which it became B&H Bank’s holding company, and elected to be a financial holding company in September 2023. As a bank holding company that has elected to be a financial holding company, Burke & Herbert is subject to regulation and supervision by the Federal Reserve. Burke & Herbert has no material operations and owns 100% of B&H Bank. B&H Bank is a Virginia-chartered commercial bank that commenced operations in 1852. B&H Bank is supervised and regulated by the FDIC and the VBFI.

Burke & Herbert is a community-oriented financial institution that seeks to be the provider of choice for financial solutions to customers who value exceptional personalized service, local decision making, and modern banking technology. Burke & Herbert’s business involves attracting deposits from local businesses and individual customers and using these deposits to originate commercial, mortgage, and consumer loans in its market area. It also invests in securities consisting primarily of obligations of U.S. government-sponsored entities, municipal obligations, mortgage-backed securities issued by Fannie Mae, Freddie Mac and Ginnie Mae, and the subordinated debt of other financial institutions. Burke & Herbert is the owner and beneficiary of company-owned life insurance policies on certain current and former B&H Bank employees. These policies generate income and can be liquidated, if necessary, with associated tax costs.

Burke & Herbert is focused on growing business relationships and building core deposits, profitable loans and non-interest income. It believes that it has a solid franchise that meets the financial needs of its clients and communities by providing an array of personalized products and services delivered by seasoned professionals with decisions made at the local level. Burke & Herbert strives to be the leading community bank in its markets.

The Federal Reserve, the FDIC, and the VBFI conduct periodic onsite and offsite examinations. Burke & Herbert must comply with a wide variety of reporting requirements and banking regulations. The laws and regulations governing Burke & Herbert generally have been promulgated to protect depositors and the federal deposit insurance funds and not to protect shareholders. Additionally, Burke & Herbert must bear the cost of compliance with the reporting required by these regulations; which costs can be significant and may have an effect on Burke & Herbert’s financial performance.

Additional information about Burke & Herbert and B&H Bank is included in the annexes to this joint proxy statement/prospectus. See the section entitled “Where You Can Find More Information” on page 176 for details about where you can find more information about Burke & Herbert.

Summit

Summit is a $4.6 billion financial holding company headquartered in Moorefield, West Virginia incorporated on March 5, 1987. Summit provides community banking services throughout West Virginia, the greater Washington, D.C. metropolitan area, Virginia, Kentucky, and the Eastern Shore of Maryland and Delaware. Summit provides these services through its community bank subsidiary, SCB.

Summit provides a wide range of community banking services, including demand, savings and time deposits; commercial, real estate and consumer loans; trust and wealth management services; and cash management services. The deposits of SCB are insured by the FDIC. To compete with other financial service providers, Summit principally relies upon personal relationships established by Summit’s officers, directors and employees with its clients and specialized services tailored to meet its clients’ needs. Summit maintains a strong community orientation by, among other things, supporting the active participation of staff members in local charitable, civic, school, religious and community development activities. Summit also has a marketing program that primarily utilizes local radio and newspapers to advertise. Banking, like most industries, is becoming more dependent on technology as a means of marketing to customers, including online and mobile banking, which Summit also uses. This approach, coupled with continuity of service by the same staff members, enables Summit and SCB to develop long-term customer relationships, maintain high quality service and respond quickly to customer needs. Summit believes that

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its emphasis on local relationship banking, together with a prudent approach to lending, are important factors in its success and growth.

Summit’s primary lending focus is providing commercial loans to local businesses with annual sales generally up to $150 million and providing owner-occupied real estate loans to individuals. Summit typically does not seek credit relationships of more than $35 million but will consider larger lending relationships exhibiting above-average credit quality. Under its commercial banking strategy, Summit focuses on offering a broad line of financial products and services to small and medium-sized businesses through full-service banking offices. SCB has senior management with extensive lending experience. These managers exercise substantial authority over credit and pricing decisions, subject to loan committee approval for larger credits.

Summit’s principal executive offices are located at 300 N. Main Street, Moorefield, WV 26836, its phone number is (304) 530-1000 and its website is www.summitfgi.com.

Summit operates 54 full-service offices — 30 located throughout West Virginia, 9 throughout Maryland, 13 throughout Northern Virginia and 1 office in each of Delaware and Kentucky.

For more information regarding Summit, please see Summit’s Annual Report on Form 10-K for the year ended December 31, 2022, its quarterly report on Form 10-Q for the quarter ended June 30, 2023, and its proxy statement for its 2023 annual meeting of shareholders, each of which are incorporated into this joint proxy statement/prospectus by reference. See “Where You Can Find More Information” on page 176, for details about the material Summit incorporates by reference into this joint proxy statement/prospectus.

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THE MERGER

This section of the joint proxy statement/prospectus describes material aspects of the merger. This summary may not contain all of the information that is important to you. You should carefully read this entire joint proxy statement/prospectus and the other documents we refer you to for a more complete understanding of the merger. In addition, we incorporate important business and financial information about each of us into this document by reference. You may obtain the information incorporated by reference into this document without charge by following the instructions in the section entitled “Where You Can Find More Information” beginning on page 176.

Terms of the Merger

Each of Burke & Herbert’s and Summit’s respective board of directors has unanimously approved the merger agreement. The merger agreement provides that, pursuant to the terms and subject to the conditions set forth in the merger agreement, Summit will merge with and into Burke & Herbert, with Burke & Herbert as the continuing corporation (such transaction is hereinafter referred to as the merger). Immediately following the merger, SCB will merge with and into B&H Bank, with B&H Bank as the continuing bank (such transaction is hereinafter referred to as the bank merger).

Each share of Summit common stock issued and outstanding immediately prior to the effective time, except for certain shares owned by Burke & Herbert or Summit (subject to certain exceptions described in the merger agreement), will be converted into the right to receive 0.5043 shares of Burke & Herbert common stock. Summit shareholders who would otherwise be entitled to a fraction of a share of Burke & Herbert common stock in the merger will instead receive, for the fraction of a share, an amount in cash (rounded to the nearest cent) based on the Burke & Herbert closing share value.

Each share of Summit series 2021 preferred stock issued and outstanding immediately prior to the effective time shall automatically be converted into the right to receive a share of a newly created series of preferred stock of Burke & Herbert having rights, preferences, privileges and voting powers and limitations and restrictions that are not materially less or more favorable to the holders of the Summit series 2021 preferred stock (taking into account that Summit will not be the surviving entity in the merger and any adjustment to the right of optional redemption by Burke & Herbert that is reasonably necessary to obtain Tier 1 Capital treatment from the Federal Reserve for such preferred stock) and, upon such conversion, the Summit series 2021 preferred stock shall no longer be outstanding and shall automatically be cancelled and retired and shall cease to exist as of the effective time and no consideration shall be issued in exchange therefor.

Burke & Herbert shareholders are being asked to approve the Burke & Herbert merger proposal and Summit shareholders are being asked to approve the Summit merger proposal. See the section entitled “The Merger Agreement” beginning on page 115 for additional and more detailed information regarding the legal documents that govern the merger, including information about the conditions to the completion of the merger and the provisions for terminating or amending the merger agreement.

Background of the Merger

As part of the ongoing oversight and management of their respective companies, each of the Burke & Herbert and Summit boards and executive management teams regularly review and assess their respective companies’ long-term strategic goals and opportunities. Each board and management team reviews and assesses their respective companies’ performance and prospects in light of competitive and other relevant developments, as they seek to enhance value for their respective shareholders and deliver the best possible services to their respective customers and communities. For each company, these reviews have included periodic discussions regarding potential transactions that could further their strategic objectives and the potential benefits and risks of any such transactions. For Summit, at certain points in the past, these discussions have resulted in completed strategic transactions.

The boards and executive management teams of Burke & Herbert and Summit have regularly reviewed and assessed various business strategies and objectives and considered various options to enhance shareholder value and the liquidity of their respective companies’ stock, as well as expand product and service offerings to align more closely with the changing demographics and economy in the markets that they serve. With respect to Summit, these

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reviews and discussions have included possible strategic transactions available to Summit, such as mergers of equals and potential acquisitions of, and business combinations with, other financial institutions.

On September 12, 2021, representatives of D.A. Davidson introduced Bradford E. Ritchie, President of SCB, and Phillip Quintana, SCB’s Regional President for Northern Virginia, to David P. Boyle, President and Chief Executive Officer of Burke & Herbert and B&H Bank, at a dinner event during the Virginia Bankers Association Convention in Charleston, South Carolina. The parties discussed their respective financial institutions, the state of the financial services industry, potential loan participation opportunities and the possibility of considering a merger of equals.

On October 1, 2021, Mr. Boyle met with H. Charles Maddy, III, President and Chief Executive Officer of Summit and Chief Executive Officer of SCB, and Robert S. Tissue, Executive Vice President and Chief Financial Officer of Summit and SCB, at Summit’s headquarters in Moorefield, West Virginia to discuss the respective banks, loan participations and whether there was desire to explore a merger of equals. In this discussion, Mr. Boyle proposed that the continuing corporation would (i) retain the Burke & Herbert brand, (ii) maintain a significant portion of its operations in Moorefield, West Virginia, (iii) be led primarily by the current management of Burke & Herbert, (iv) have legacy Burke & Herbert directors hold a majority of the positions on the board of directors of the continuing corporation, and (v) have a pro forma ownership percentage in the continuing corporation at closing for Summit’s common shareholders of approximately 46.0%.

At the Summit board of directors meeting on October 21, 2021, Mr. Maddy reported on the October 1 meeting with Mr. Boyle and the proposed merger terms discussed in that meeting. Following its discussion of Mr. Boyle’s proposal, the Summit board of directors decided not to pursue the proposed merger of equals at the time because the terms were not consistent with the board’s strategic goals for Summit, including the proposed pro forma ownership percentage of Summit’s common shareholders in the continuing corporation and the board’s desire that a merger of equals be structured to retain Summit management in significant roles.

On November 29, 2021, Mr. Maddy met with Mr. Boyle in Alexandria, Virginia to communicate the Summit board’s view with respect to their prior discussions and discuss further the respective businesses, the banking industry generally and the long-term strategic goals of both companies. On February 3, 2022, Mr. Maddy met with Mr. Boyle and Roy E. Halyama, Executive Vice President and Chief Financial Officer of Burke & Herbert, in Alexandria, Virginia and continued discussions regarding the banking industry, the compatibility of the two organizations and a potential merger of equals.

On February 24, 2022, Mr. Maddy reported to the Summit board of directors that discussions continued with Burke & Herbert regarding a potential merger of equals. The Summit board of directors discussed a variety of aspects of the potential merger and Burke & Herbert, including the fact that Burke & Herbert’s headquarters in Alexandria, Virginia and footprint in the greater Washington, D.C. metropolitan area place Burke & Herbert in a desirable growth market. The Summit board of directors noted that following the initial discussion with Mr. Boyle regarding potential merger terms, Mr. Boyle indicated that he recognized Summit’s low overhead expense as a core strength and indicated a continued willingness to keep a significant portion of the continuing corporation’s operations in Moorefield, West Virginia. The Summit board authorized Summit management to further investigate a potential merger of equals with Burke & Herbert.

On February 24, 2022, Mr. Boyle reported to the Burke & Herbert board of directors that discussions had occurred with Summit regarding a potential merger of equals. The Burke & Herbert board of directors discussed a variety of aspects of the potential merger and Summit, including the fact that Summit’s attractive geographic footprint included markets that Burke & Herbert has not historically served but had evaluated for future expansion opportunities as well as Summit’s low operational overhead and access to low-cost deposits. The Burke & Herbert board authorized Burke & Herbert management to further investigate a merger of equals with Summit.

On March 8, 2022, Summit and Burke & Herbert received preliminary pro forma information regarding a potential merger of equals between the two companies compiled by D.A. Davidson, which would subsequently be engaged by Summit to act as its financial advisor.

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On March 24, 2022, Mr. Maddy provided the Summit board of directors with an update on discussions with Burke & Herbert and indicated that D.A. Davidson had recently compiled preliminary pro forma information regarding a potential merger of equals between the two companies. Following its discussion, the Summit board affirmed its interest in pursuing a potential merger of equals with Burke & Herbert.

Also on March 24, 2022, Mr. Boyle informed the Burke & Herbert board that conversations with Summit concerning a merger of equals were continuing.

Messrs. Boyle and Halyama met with Messrs. Maddy and Tissue on March 28, 2022 at Summit’s corporate offices in Moorefield, West Virginia to discuss further the terms of a potential merger of equals. At this meeting, the representatives of the parties were unable to reach consensus on the financial terms of the potential merger, including the pro rata ownership of the continuing corporation among the two shareholder groups, corporate governance terms, and key management roles, and conversations regarding a potential merger of equals transaction between the companies stalled.

On May 17, 2022, a representative of D.A. Davidson met with Messrs. Maddy and Tissue in Moorefield, West Virginia to revisit the potential terms of and prospects with respect to a potential merger of equals between Summit and Burke & Herbert.

On June 23, 2022, Mr. Boyle provided the Burke & Herbert board of directors with an update regarding the discussions with Summit, including that no consensus was reached on significant aspects of the proposed transaction and that communications had again stalled.

On August 24, 2022, representatives of D.A. Davidson communicated the information discussed with Messrs. Maddy and Tissue on May 17, 2022 to Messrs. Boyle and Halyama and sought to obtain their views with respect to the potential merger of equals.

Messrs. Maddy and Tissue met with a representative of D.A. Davidson again on October 5, 2022, in Louisville, Colorado and discussed a framework for a potential merger of equals between Summit and Burke & Herbert and social and governance aspects related to such a merger.

In mid-January 2023, representatives of D.A. Davidson spoke separately with Mr. Tissue and Messrs. Boyle and Halyama, each of whom indicated their institution’s willingness to consider reengaging in conversations with respect to a potential merger of equals.

On January 26, 2023, Mr. Maddy reported to the Summit board of directors that he had recently been contacted by Mr. Boyle, who stated that he would like to have another meeting with Messrs. Maddy and Tissue regarding a potential merger of equals. Mr. Boyle indicated that Burke & Herbert was in the process of being listed on the Nasdaq stock exchange. Following its discussion, the Summit board instructed Summit management to continue discussions regarding a potential merger of equals with Burke & Herbert.

On February 28, 2023, Messrs. Maddy and Tissue met with Messrs. Boyle and Halyama at Summit’s branch office in Winchester, Virginia. During this meeting, Mr. Boyle proposed broad merger terms, including a potential pro forma ownership range for Summit’s common shareholders in the continuing corporation that would be closer to 50% than previously proposed.

On March 6, 2023, Messrs. Tissue and Halyama met in Alexandria, Virginia to discuss the business operations and systems of the two companies and their respective business philosophies.

Mr. Maddy reported the substance of the February 28 meeting to the Summit board of directors on March 23, 2023. The Summit board of directors agreed to reengage in discussions with Burke & Herbert regarding a potential merger of equals, beginning with a meeting among certain members of each of the respective boards to be held in April 2023.

Messrs. Maddy and Tissue convened a meeting with Messrs. Boyle and Halyama and four respective board representatives of each of Summit and Burke & Herbert in Haymarket, Virginia on April 25, 2023. Burke & Herbert’s common stock began trading on the Nasdaq Capital Market on April 26, 2023.

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On April 27, 2023, the Summit board of directors discussed the April 25 joint meeting, including the similar business cultures and philosophies of the two companies, and considered the potential terms of the proposed merger, including the management of the continuing corporation, the headquarters of the continuing corporation and the continuing bank, and the fact that a significant portion of the operations of the continuing bank were expected to remain in Moorefield, West Virginia following completion of the proposed merger. The Summit board also discussed the potential impact of having a larger market capitalization for the continuing corporation. Following such discussion, the Summit board of directors unanimously authorized Summit management to continue discussions with the goal of developing a term sheet between the parties.

Also on April 27, 2023, Mr. Boyle updated the Burke & Herbert board of directors with respect to the discussions with Summit. At such meeting, the Burke & Herbert board of directors discussed the potential terms of the merger including the proposed ownership split in the continuing corporation upon completion of the merger, the management of the continuing corporation, the headquarters of the continuing corporation and the continuing bank, and the fact that a significant portion of the operations of the continuing bank would remain in Moorefield, West Virginia following completion of the proposed merger. Following such discussion, the Burke & Herbert board of directors unanimously authorized Burke & Herbert management to continue discussions with the goal of developing a term sheet between the parties.

Burke & Herbert presented a non-binding preliminary term sheet to Summit on May 2, 2023.

On May 12, 2023, Burke & Herbert and Summit executed a mutual nondisclosure agreement in connection with the proposed transaction to facilitate potential due diligence between the parties.

On May 18, 2023, the Burke & Herbert board of directors met to discuss the terms of the non-binding preliminary term sheet, merger of equals transactions generally and the proposed merger with Summit. Representatives of Burke & Herbert’s financial advisor, KBW, and Burke & Herbert’s counsel, Troutman Pepper Hamilton Sanders LLP (“Troutman Pepper”), also participated in this meeting. Troutman Pepper discussed the board’s fiduciary duties and the standard of director conduct under Virginia law in the context of a merger of equals. The Burke & Herbert board of directors authorized Burke & Herbert’s management to continue to negotiate the proposed merger of equals with Summit on the terms and conditions indicated in the preliminary, non-binding term sheet.

On May 25, 2023, the Summit board of directors reviewed the terms of the non-binding preliminary term sheet, including the anticipated continuing corporation ownership range of 48.00% to 49.50% for Summit common shareholders following the proposed merger, the proposed composition of the board of directors of the continuing corporation, seven seats of which would be allocated to Summit directors and eight of which would be allocated to Burke & Herbert directors, anticipated senior management roles for the continuing corporation and the continuing bank, including key roles for Messrs. Maddy and Tissue, the maintenance of a significant portion of the operations of the continuing bank in Moorefield, West Virginia, and employee retention following the merger. The Summit board also discussed Burke & Herbert’s recent share price, anticipated deal protections and other general potential risks related to the proposed merger of equals. Following the discussion, the Summit board of directors unanimously approved the non-binding term sheet. Thereafter, Mr. Maddy communicated this news to Mr. Boyle.

On May 26, 2023, Mr. Boyle updated the Burke & Herbert board of directors at a telephonic meeting with respect to the Summit approval of the non-binding term sheet and reviewed the terms contained therein.

On May 30, 2023, Summit and Burke & Herbert executed the non-binding term sheet, which included a potential pro forma ownership range for Summit’s common shareholders in the combined corporation of 48.00% to 49.50%.

On May 31, 2023, Summit engaged D.A. Davidson to serve as its financial advisor with respect to the proposed merger of equals with Burke & Herbert.

Throughout June 2023, Summit and Burke & Herbert conducted a thorough due diligence review of the other company’s operations, assets and liabilities. Summit and Burke & Herbert jointly engaged a third-party consultant with expertise in bank merger transactions to perform targeted due diligence of each party’s loan portfolio. On June

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6, 2023, Messrs. Boyle and Halyama and Burke & Hebert’s vice chair S. Laing Hinson met with Messrs. Maddy and Tissue and Summit’s chair Oscar M. Bean in Front Royal, Virginia to discuss the potential surviving corporation’s culture, corporate systems, governance, management team, board composition, and the steps necessary to reach a definitive agreement with respect the proposed merger of equals. On June 22, 2023, Messrs. Boyle and Halyama met with Messrs. Maddy and Tissue in Ashburn, Virginia and preliminarily agreed on the personnel who would fill certain top management positions for the continuing corporation.

On June 23, 2023, Troutman Pepper circulated an initial draft of the merger agreement to Summit’s counsel, Bowles Rice LLP (“Bowles Rice”).

During its regular board meetings on June 29, 2023 and July 27, 2023, Summit management provided the Summit board of directors with updates on the status of negotiations with Burke & Herbert and the due diligence process. The board considered market trends, the recent financial performance of Summit and Burke & Herbert and recent developments with respect to the stock prices of Summit and Burke & Herbert. The board supported management’s negotiating positions in the ongoing discussions with Burke & Herbert, particularly management’s position that, in light of the recent decline in Burke & Herbert’s stock price, Summit shareholders should own 49.50% of the continuing corporation, which was the upper end of the range proposed in the non-binding term sheet.

From the period beginning June 23, 2023 through August 23, 2023, representatives of Bowles Rice and Troutman Pepper exchanged several additional drafts of the merger agreement and related transaction documents, and members of Burke & Herbert and Summit executive management, with the assistance of their respective legal and financial advisors, continued to negotiate the outstanding terms of the merger agreement, including at an in-person meeting among Messrs. Maddy and Tissue and Messrs. Boyle and Halyama on August 7, 2023 in Alexandria, Virginia. Negotiations during this period focused, among other things, on the pro rata ownership of the continuing corporation among the two shareholder groups, the personnel from each company who would fill key management positions, the terms of certain employee benefit programs, the number of legacy directors from each company who would comprise the board of directors of the continuing corporation, and deal protection provisions contained in the merger agreement. As a result of these negotiations, certain terms of the transaction reflected in the merger agreement changed from those proposed in the executed, non-binding term sheet, including (i) an increase in the resulting ownership split of the continuing corporation for Summit’s common shareholders to 49.90% ownership of the combined corporation, (ii) an additional Summit director was added to the boards of each of the continuing corporation and the continuing bank, bringing the total to eight continuing directors from each party, and (iii) an additional termination right was added in the event that either party is in receipt of a superior alternative proposal and not in breach of the nonsolicitation covenants. Also, during this period, Burke & Herbert and Summit continued to conduct reciprocal due diligence, including on July 12, 2023, when the parties’ respective credit due diligence was reviewed and discussed on August 15, 2023, when senior management representatives of Summit and Burke & Herbert met in Haymarket, Virginia.

During August 2023, B&H Bank negotiated individual employment agreements with Messrs. Maddy and Tissue, and Bradford E. Ritchie, the President of SCB, in connection with the execution of the merger agreement that would take effect at the closing of the merger. Burke & Herbert believed the retention of these officers was crucial for the continuity required to achieve the strategic benefits of the merger.

On August 16, 2023, the Summit board of directors convened a special meeting to discuss mergers of equals transactions generally and the proposed merger of equals with Burke & Herbert. The Summit board also reviewed certain key terms of the proposed merger agreement. Members of Summit’s senior management team were in attendance and representatives of D.A. Davidson and Bowles Rice also participated in the meeting.

On August 21, 2023, representatives of D.A. Davidson and KBW discussed the computation of the exchange ratio in the merger agreement, which resulted in an exchange ratio of 0.5043 to reflect the pro-rata ownership of the continuing corporation of the two groups of shareholders as agreed upon by the parties.

On August 24, 2023, Summit convened its regular board meeting to discuss the proposed merger with Burke & Herbert and review the terms of the proposed merger agreement and related documents. Members of the Summit senior management team were in attendance and representatives of D.A. Davidson and Bowles Rice also

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participated in the meeting. The Summit board was provided with copies of the merger agreement, the bank merger agreement, the affiliate agreements and a summary of the material terms of the merger agreement and the proposed merger prepared by Bowles Rice. At this meeting, the Summit board discussed the proposed exchange ratio and operations of the continuing corporation, including key management roles for Summit officers and the continuing corporation’s commitment to an operations center in Moorefield, West Virginia for the continuing bank. The Summit board also discussed the proposed employment arrangements between B&H Bank and each of Messrs. Maddy, Tissue and Ritchie, and the fact that each executive intended to enter into an employment agreement with B&H Bank in connection with the execution of the merger agreement (contingent on closing).

Also at this meeting, representatives of D.A. Davidson reviewed the financial aspects of the proposed merger and rendered to the Summit board of directors an opinion (which was initially rendered verbally and then confirmed in a written opinion, dated August 24, 2023, a copy of which is attached to this joint proxy statement/prospectus as Annex C) to the effect that, as of that date and subject to the procedures followed, assumptions made and matters considered, and qualifications and limitations on the review undertaken by D.A. Davidson as set forth in such opinion, the exchange ratio was fair, from a financial point of view, to the holders of Summit common stock. Representatives of Bowles Rice discussed the terms of the merger agreement, the bank merger agreement, the affiliate agreements and related transaction documents with the Summit board, and updated the Summit board with respect to negotiations on the terms of the merger and discussed the board’s fiduciary duties and the standard of director conduct under West Virginia law. Members of Summit’s senior management team reviewed the strategic benefits of the proposed merger with Burke & Herbert, including the business and financial prospects of the continuing corporation, along with the social and economic effects of the proposed merger on Summit’s employees, depositors and customers and the communities in which Summit operates.

After considering the proposed terms of the merger agreement and the mergers and the related transaction documents, and taking into consideration the matters discussed during that meeting and prior meetings of the Summit board of directors, including the factors described under the section of this joint proxy statement/prospectus entitled “The Merger—Summit’s Reasons for the Merger and Recommendation of the Summit Board” on page 76, the Summit board determined that the merger agreement, including the merger and the other transactions contemplated thereby, was in the best interests of Summit and its shareholders, and the Summit board unanimously approved and adopted the merger agreement and the mergers and the other transactions contemplated thereby. Immediately thereafter, the SCB board of directors unanimously approved and adopted the bank merger agreement and unanimously approved the bank merger.

On August 24, 2023, the Burke & Herbert board of directors convened a special meeting to discuss the proposed merger with Summit and review the terms of the proposed merger agreement and related documents. Members of the Burke & Herbert senior management team were in attendance and representatives of KBW and Troutman Pepper also participated in the meeting. The Burke & Herbert board was provided with copies of the merger agreement, the bank merger agreement, the affiliate agreements and a summary of the material terms of the merger agreement and the proposed merger prepared by Troutman Pepper. At this meeting, the Burke & Herbert board discussed the terms of the proposed merger and the strategic reasons for the merger, including the prospects for growth of the combined company and the cultural similarities between the two companies that would be expected to facilitate an efficient and effective integration. The Burke & Herbert board also discussed the proposed employment arrangements between B&H Bank and each of Messrs. Maddy, Tissue and Ritchie, and the fact that each executive intended to enter into an employment agreement with B&H Bank in connection with the execution of the merger agreement (contingent on closing).

Also at this meeting, KBW reviewed the financial aspects of the proposed merger and rendered to the Burke & Herbert board of directors an opinion (which was initially rendered verbally and then confirmed in a written opinion, dated August 24, 2023, a copy of which is attached to this joint proxy statement/prospectus as Annex B) to the effect that, as of that date and subject to the procedures followed, assumptions made, matters considered, and qualifications and limitations on the review undertaken by KBW as set forth in such opinion, the exchange ratio in the proposed merger was fair, from a financial point of view, to Burke & Herbert. Troutman Pepper discussed the terms of the merger agreement, the bank merger agreement, the affiliate agreements and related transaction documents with the Burke & Herbert board, and updated the Burke & Herbert board with respect to certain due diligence matters and the negotiations on the terms of the merger, and summarized the prior discussion regarding the

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board’s fiduciary duties and the standard of director conduct under Virginia law. Members of Burke & Herbert’s senior management team reviewed the strategic benefits of the proposed merger with Summit, including the business and financial prospects of the continuing corporation, along with the operational, social and economic effects of the proposed merger on Burke & Herbert’s employees, depositors and customers and the communities in which Burke & Herbert operates.

After considering the proposed terms of the merger agreement and the mergers and the related transaction documents, and taking into consideration the matters discussed during that meeting and prior meetings of the Burke & Herbert board of directors, including the factors described under the section of this joint proxy statement/prospectus entitled “—Burke & Herbert’s Reasons for the Merger and Recommendation of the Burke & Herbert Board” on page 62, the Burke & Herbert board determined that the merger agreement, including the mergers and the other transactions contemplated thereby, was in the best interests of Burke & Herbert and its shareholders, and the Burke & Herbert board unanimously approved and adopted the merger agreement and the mergers and the other transactions contemplated thereby. Immediately thereafter, the B&H Bank board of directors unanimously approved and adopted the bank merger agreement and unanimously approved the bank merger.

Following the meetings of the Burke & Herbert and Summit boards and the close of markets on August 24, 2023, Burke & Herbert and Summit executed the merger agreement. Each director of Burke & Herbert and Summit executed an affiliate agreement containing voting obligations with respect to the proposed merger and certain additional support commitments, and Messrs. Maddy, Tissue and Ritchie each executed an individual employment agreement (contingent on completion of the merger) with B&H Bank. Burke & Herbert and Summit issued a joint press release announcing the execution of the merger agreement.

Burke & Herbert’s Reasons for the Merger; Recommendation of Burke & Herbert’s Board of Directors

After careful consideration, the Burke & Herbert board of directors, at a special meeting on August 24, 2023, unanimously (i) determined that the merger agreement and the transactions contemplated thereby, including the merger and the issuance of Burke & Herbert common stock, are advisable and fair to and in the best interests of Burke & Herbert and its shareholders, (ii) approved and adopted the merger agreement, and the transactions contemplated thereby (including the merger, the issuance of Burke & Herbert common stock, and the bank merger) and (iii) recommended the approval by Burke & Herbert shareholders of the Burke & Herbert merger proposal and the other matters to be voted on at the Burke & Herbert special meeting.

In reaching this decision, the Burke & Herbert board of directors evaluated the merger agreement, the bank merger and the other matters contemplated by the merger agreement in consultation with Burke & Herbert’s senior management, as well as with Burke & Herbert’s legal and financial advisors, and considered a number of factors, including the following:

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The Burke & Herbert board of directors also considered potential risks related to the proposed transaction. The board concluded that the anticipated benefits of combining with Summit were likely to outweigh these risks substantially. These potential risks included:

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The foregoing discussion of the information and factors considered by the Burke & Herbert board of directors is not intended to be exhaustive, but includes the material factors considered by the board. In reaching its decision to approve the merger agreement and the transactions contemplated by the merger agreement, the Burke & Herbert board of directors did not quantify or assign any relative weights to the factors considered, and individual directors may have given different weights to different factors. The board considered all these factors as a whole, including through discussions with Burke & Herbert’s management and Burke & Herbert’s outside financial and legal advisors, and overall considered the factors to support its determination.

For the reasons set forth above, the Burke & Herbert board of directors determined that the merger agreement and the transactions contemplated thereby (including the bank merger) are advisable and fair to and in the best interests of Burke & Herbert and its shareholders.

Certain of Burke & Herbert’s directors and executive officers have other interests in the merger that are different from, or in addition to, those of Burke & Herbert’s shareholders generally, as discussed under the caption “—Interests of Certain Burke & Herbert Directors and Executive Officers in the Merger,” below. The Burke & Herbert board of directors was aware of and considered these potential interests, among other matters, in evaluating the merger and in making its recommendation to Burke & Herbert shareholders.

It should be noted that this explanation of the reasoning of the Burke & Herbert board of directors and all other information presented in this section is forward-looking in nature and, therefore, should be read in light of the factors discussed in the section entitled “Cautionary Statement Regarding Forward-Looking Statements” on page 29.

Opinion of Burke & Herbert’s Financial Advisor

Burke & Herbert engaged KBW to render financial advisory and investment banking services to Burke & Herbert, including an opinion to the Burke & Herbert board as to the fairness, from a financial point of view, to Burke & Herbert of the exchange ratio in the proposed merger. Burke & Herbert selected KBW because KBW is a nationally recognized investment banking firm with substantial experience in transactions similar to the proposed merger. As part of its investment banking business, KBW is continually engaged in the valuation of banks and bank holding companies and their securities in connection with mergers and acquisitions.

As part of its engagement, representatives of KBW attended the meeting of the Burke & Herbert board held on August 24, 2023 at which the Burke & Herbert board evaluated the proposed merger. At this meeting, KBW reviewed the financial aspects of the proposed merger and rendered an opinion to the Burke & Herbert board of directors to the effect that, as of such date and subject to the procedures followed, assumptions made, matters considered, and qualifications and limitations on the review undertaken by KBW as set forth in such opinion, the exchange ratio in the proposed merger was fair, from a financial point of view, to Burke & Herbert. The Burke & Herbert board of directors approved the merger agreement at this meeting.

The description of the opinion set forth herein is qualified in its entirety by reference to the full text of the opinion, which is attached as Annex B to this document and is incorporated herein by reference, and describes the procedures followed, assumptions made, matters considered, and qualifications and limitations on the review undertaken by KBW in preparing the opinion.

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KBW’s opinion speaks only as of the date of the opinion. The opinion was for the information of, and was directed to, the Burke & Herbert board (in its capacity as such) in connection with its consideration of the financial terms of the merger. The opinion addressed only the fairness, from a financial point of view, of the exchange ratio in the merger to Burke & Herbert. It did not address the underlying business decision of Burke & Herbert to engage in the merger or enter into the merger agreement or constitute a recommendation to the Burke & Herbert board of directors in connection with the merger, and it does not constitute a recommendation to any holder of Burke & Herbert common stock or any shareholder of any other entity as to how to vote in connection with the merger or any other matter, nor does it constitute a recommendation regarding whether or not any such shareholder should enter into a voting, shareholders’, affiliates’ or other agreement with respect to the merger or exercise any dissenters’ or appraisal rights that may be available to such shareholder.

KBW’s opinion was reviewed and approved by KBW’s Fairness Opinion Committee in conformity with its policies and procedures established under the requirements of Rule 5150 of the Financial Industry Regulatory Authority.

In connection with the opinion, KBW reviewed, analyzed and relied upon material bearing upon the financial and operating condition of Burke & Herbert and Summit and bearing upon the merger, including, among other things:

KBW’s consideration of financial information and other factors that it deemed appropriate under the circumstances or relevant to its analyses included, among others, the following:

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KBW also performed such other studies and analyses as it considered appropriate and took into account its assessment of general economic, market and financial conditions and its experience in other transactions, as well as its experience in securities valuation and knowledge of the banking industry generally. KBW also participated in discussions that were held by the managements of Burke & Herbert and Summit regarding the past and current business operations, regulatory relations, financial condition and future prospects of their respective companies and such other matters as KBW deemed relevant to its inquiry.

In conducting its review and arriving at its opinion, KBW relied upon and assumed the accuracy and completeness of all of the financial and other information provided to or discussed with it or that was publicly available and KBW did not independently verify the accuracy or completeness of any such information or assume any responsibility or liability for such verification, accuracy or completeness. KBW relied upon Burke & Herbert management as to the reasonableness and, as applicable, the achievability of the publicly available consensus “street estimates” of Summit, the adjustments thereto, the assumed long-term growth rates for Summit, the financial and operating forecasts and projections of Burke & Herbert, and the estimates regarding certain pro forma financial effects of the merger on Burke & Herbert (including, without limitation, the cost savings expected to result or be derived from the merger), all as referred to above (and the assumptions and bases for all such information), and KBW assumed that all such information was reasonably prepared and represented, or in the case of the publicly available consensus “street estimates” of Summit referred to above, that such estimates were consistent with the best currently available estimates and judgments of Burke & Herbert management and that the forecasts, projections and estimates reflected in such information (as adjusted by Burke & Herbert management in the case of the publicly available consensus “street estimates” of Summit) would be realized in the amounts and in the time periods currently estimated.

It is understood that the portion of the foregoing financial information of Burke & Herbert and Summit that was provided to KBW was not prepared with the expectation of public disclosure and that all of the foregoing financial information, including the publicly available consensus “street estimates” of Summit, was based on numerous variables and assumptions that are inherently uncertain (including, without limitation, factors related to general economic and competitive conditions and, in particular, the widespread disruption, extraordinary uncertainty and unusual volatility arising from global tensions and political unrest, economic uncertainty, inflation, rising interest rates, the COVID-19 pandemic and, in the case of the banking industry, recent actual or threatened regional bank failures, including the effect of evolving governmental interventions and non-interventions) and, accordingly, actual results could vary significantly from those set forth in such information. KBW assumed, based on discussions with the management of Burke & Herbert and with the consent of the Burke & Herbert board, that all such information provided a reasonable basis upon which KBW could form its opinion and KBW expressed no view as to any such information or the assumptions or bases therefor. KBW relied on all such information without independent verification or analysis and did not in any respect assume any responsibility or liability for the accuracy or completeness thereof.

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KBW also assumed that there were no material changes in the assets, liabilities, financial condition, results of operations, business or prospects of either Burke & Herbert or Summit since the date of the last financial statements of each such entity that were made available to KBW. KBW is not an expert in the independent verification of the adequacy of allowances for loan and lease losses and KBW assumed, without independent verification and with Burke & Herbert’s consent, that the aggregate allowances for loan and lease losses for each of Burke & Herbert and Summit are adequate to cover such losses. In rendering its opinion, KBW did not make or obtain any evaluations or appraisals or physical inspection of the property, assets or liabilities (contingent or otherwise) of Burke & Herbert or Summit, the collateral securing any of such assets or liabilities, or the collectability of any such assets, nor did KBW examine any individual loan or credit files, nor did it evaluate the solvency, financial capability or fair value of Burke & Herbert or Summit under any state or federal laws, including those relating to bankruptcy, insolvency or other matters. KBW made note of the classification by each of Burke & Herbert and Summit of its loans and owned securities as either held to maturity or held for investment, on the one hand, or held for sale, on the other hand, and also reviewed reported fair value marks-to-market and other reported valuation information, if any, relating to such loans or owned securities contained in the respective financial statements of Burke & Herbert and Summit, but KBW expressed no view as to any such matters. Estimates of values of companies and assets do not purport to be appraisals or necessarily reflect the prices at which companies or assets may actually be sold. Such estimates are inherently subject to uncertainty and should not be taken as KBW’s view of the actual value of any companies or assets.

KBW assumed, in all respects material to its analyses:

KBW assumed that the merger would be consummated in a manner that complies with the applicable provisions of the Securities Act of 1933, the Exchange Act, and all other applicable federal and state statutes, rules and regulations. KBW was further advised by representatives of Burke & Herbert that Burke & Herbert relied upon advice from its advisors (other than KBW) or other appropriate sources as to all legal, financial reporting, tax, accounting and regulatory matters with respect to Burke & Herbert, Summit, the merger and any related transaction (including the bank merger), and the merger agreement. KBW did not provide advice with respect to any such matters.

KBW’s opinion addressed only the fairness, from a financial point of view, as of the date of such opinion, of the exchange ratio in the merger to Burke & Herbert. KBW expressed no view or opinion as to any other terms or aspects of the merger or any term or aspect of any related transaction (including the bank merger), including without

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limitation, the form or structure of the merger or any such related transaction, the treatment of outstanding preferred stock and other securities of Summit in the merger, any consequences of the merger or any related transaction to Burke & Herbert, its shareholders, creditors or otherwise, or any terms, aspects, merits or implications of any employment, retention bonus, charitable, consulting, affiliate, voting, support, shareholder or other agreements, arrangements or understandings contemplated or entered into in connection with the merger, any such related transaction, or otherwise. KBW’s opinion was necessarily based upon conditions as they existed and could be evaluated on the date of the opinion and the information made available to KBW through the date hereof. There is currently significant volatility in the stock and other financial markets arising from global tensions and political unrest, economic uncertainty, inflation, rising interest rates, the COVID-19 pandemic and, in the case of the banking industry, recent actual or threatened regional bank failures, including the effect of evolving governmental interventions and non-interventions. Developments subsequent to the date of KBW’s opinion may have affected, and may affect the conclusion reached in KBW’s opinion and that KBW did not and does not have an obligation to update, revise or reaffirm its opinion. KBW’s opinion did not address, and KBW expressed no view or opinion with respect to:

In performing its analyses, KBW made numerous assumptions with respect to industry performance, general business, economic, market and financial conditions and other matters, which are beyond the control of KBW, Burke & Herbert and Summit. Any estimates contained in the analyses performed by KBW are not necessarily indicative of actual values or future results, which may be significantly more or less favorable than suggested by these analyses. Additionally, estimates of the value of businesses or securities do not purport to be appraisals or to reflect the prices at which such businesses or securities might actually be sold. Accordingly, these analyses and estimates are inherently subject to substantial uncertainty. In addition, KBW’s opinion was among several factors taken into consideration by the Burke & Herbert board of directors in making its determination to approve the

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merger agreement and the merger. Consequently, the analyses described below should not be viewed as determinative of the decision of the Burke & Herbert board of directors with respect to the fairness of the exchange ratio. The type and amount of consideration payable in the merger were determined through negotiation between Burke & Herbert and Summit and the decision of Burke & Herbert to enter into the merger agreement was solely that of the Burke & Herbert board of directors.

The following is a summary of the material financial analyses provided by KBW to the Burke & Herbert board of directors in connection with its opinion. The summary is not a complete description of the financial analyses underlying the opinion or the presentation materials provided by KBW to the Burke & Herbert board, but summarizes the material analyses performed and provided in connection with such opinion. The financial analyses summarized below include information presented in tabular format. The tables alone do not constitute a complete description of the financial analyses. The preparation of a fairness opinion is a complex analytic process involving various determinations as to appropriate and relevant methods of financial analysis and the application of those methods to the particular circumstances. Therefore, a fairness opinion is not readily susceptible to partial analysis or summary description. In arriving at its opinion, KBW did not attribute any particular weight to any analysis or factor that it considered, but rather made qualitative judgments as to the significance and relevance of each analysis and factor. Accordingly, KBW believes that its analyses and the summary of its analyses must be considered as a whole and that selecting portions of its analyses and factors or focusing on the information presented below in tabular format, without considering all analyses and factors or the full narrative description of the financial analyses, including the methodologies and assumptions underlying the analyses, could create a misleading or incomplete view of the process underlying its analyses and opinion.

For purposes of the financial analyses described below, KBW utilized an implied transaction value for the proposed merger of $25.20 per share of outstanding Summit common stock, or approximately $371.5 million in the aggregate (inclusive of the implied value of unvested restricted stock unit awards and outstanding in-the-money stock appreciation rights of Summit), based on the 0.5043x exchange ratio in the proposed merger and the closing price of Burke & Herbert common stock on August 23, 2023. In addition to the financial analyses described below, KBW reviewed with the Burke & Herbert board of directors for informational purposes, among other things, an implied transaction multiple for the proposed merger (based on the implied transaction value for the proposed merger of $25.20 per share of outstanding Summit common stock) of 6.5x Summit’s estimated 2023 earnings per share (“EPS”) using publicly available consensus “street estimates” of Summit.

Burke & Herbert and Summit Selected Companies Analysis

Using publicly available information, KBW compared the financial performance, financial condition and market performance of Burke & Herbert and Summit to 12 selected publicly-traded banks headquartered in Kentucky, Maryland, North Carolina, Ohio, Pennsylvania, Virginia and West Virginia with total assets between $2.5 billion and $5.0 billion. Merger targets, mutual holding companies and companies with total assets over $5.0 billion pro forma for pending or recently completed transactions were excluded from the selected companies.

The selected companies were as follows (shown in descending order of total assets by column):

To perform this analysis, KBW used profitability and other financial information for the most recent completed fiscal quarter (“MRQ”) or latest 12 months (“LTM”) available or as of the end of such periods and market price information as of August 23, 2023. KBW also used 2023 and 2024 EPS estimates taken from financial forecasts and projections of Burke & Herbert provided by Burke & Herbert management and publicly available consensus “street estimates” for Summit and the selected companies to the extent publicly available (consensus “street” estimates were

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not publicly available for two of the selected companies). Where consolidated holding company level financial data for the selected companies was unreported, subsidiary bank level data was utilized to calculate ratios (subsidiary bank level data necessary to calculate Total Capital Ratio was also not then publicly available for two of the selected companies). Certain financial data presented in the tables below may not correspond to the data presented in Burke & Herbert’s and Summit’s historical financial statements, or the data presented under the section “The Merger — Opinion of Summit’s Financial Advisor,” as a result of the different periods, assumptions and methods used to compute the financial data presented.

KBW’s analysis showed the following concerning the financial performance of Burke & Herbert, Summit and the selected companies:

KBW’s analysis also showed the following concerning the financial condition of Burke & Herbert, Summit and, to the extent publicly available, the selected companies:

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In addition, KBW’s analysis showed the following concerning the market performance of Burke & Herbert, Summit and, to the extent publicly available, the selected companies:

No company used as a comparison in the above selected companies analysis is identical to Burke & Herbert or Summit. Accordingly, an analysis of these results is not mathematical. Rather, it involves complex considerations and judgments concerning differences in financial and operating characteristics of the companies involved.

Selected Transactions Analysis

KBW reviewed publicly available information related to six selected U.S. whole bank and thrift transactions announced since December 31, 2020 with announced deal values between $100 million and $1.5 billion and pro forma ownership of the acquired company’s shareholders in the combined company of 40% or greater. Terminated transactions were excluded from the selected transactions.

The selected transactions were as follows:

For each selected transaction, KBW derived the following implied transaction statistics, in each case based on the transaction consideration value paid for the acquired company and using financial data based on the acquired company’s then latest publicly available financial statements prior to the announcement of the respective transaction and, to the extent publicly available, the one-year forward EPS consensus “street estimates” for the acquired company at the announcement of the respective transaction:

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KBW also reviewed the price per common share paid for the acquired company as a premium to the closing price of the acquired company one day prior to the announcement of the respective transaction (expressed as a percentage and referred to as the one-day market premium). The resulting transaction multiples and premiums for the selected transactions were compared with the corresponding transaction multiples and premiums for the proposed merger based on the implied transaction value for the merger of $25.20 per outstanding share of Summit common stock and using historical financial information for Summit as of or for the 12-month period ended June 30, 2023, publicly available consensus “street estimates” for Summit’s estimated 2024 EPS, adjustments thereto provided by Burke & Herbert management and the closing price of Summit common stock on August 23, 2023.

The results of the analysis are set forth in the following:

No company or transaction used as a comparison in the above selected transaction analysis is identical to Summit or the proposed merger. Accordingly, an analysis of these results is not mathematical. Rather, it involves complex considerations and judgments concerning differences in financial and operating characteristics of the companies involved.

Relative Contribution Analysis

KBW analyzed the relative standalone contribution of Burke & Herbert and Summit to various pro forma balance sheet and income statement items and the combined market capitalization of the continuing corporation. This analysis did not include purchase accounting adjustments or cost savings. To perform this analysis, KBW used (i) balance sheet data for Burke & Herbert and Summit as of June 30, 2023, (ii) financial forecasts and projections of Burke & Herbert provided by Burke & Herbert management, (iii) publicly available consensus “street estimates” of Summit as well as certain adjustments thereto provided by Burke & Herbert management, and (iv) market price information as of August 23, 2023. The results of KBW’s analysis are set forth in the following table, which also compares the results of KBW’s analysis with the respective implied pro forma ownership percentages of Burke & Herbert shareholders and Summit shareholders in the continuing corporation based on the 0.5043x exchange ratio provided for in the merger agreement:

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Financial Impact Analysis

KBW performed a pro forma financial impact analysis that combined projected income statement and balance sheet information of Burke & Herbert and Summit. Using (i) closing balance sheet estimates assumed as of December 31, 2023 for Burke & Herbert provided by Burke & Herbert management and closing balance sheet estimates assumed as of December 31, 2023 for Summit extrapolated from publicly available consensus “street estimates” of Summit, (ii) financial forecasts and projections for Burke & Herbert provided by Burke & Herbert management, (iii) publicly available consensus “street estimates” of Summit as well as certain adjustments thereto and assumed long-term growth rates for Summit provided by Burke & Herbert management, and (iv) pro forma assumptions (including, without limitation, the cost savings expected to result or be derived from the merger, certain purchase accounting and other merger-related adjustments and restructuring charges assumed with respect thereto and assumptions regarding the sale of interest rate hedges of Summit and the redemption of trust preferred securities of Summit) provided by Burke & Herbert management. KBW analyzed the potential financial impact of the merger on certain projected financial results of Burke & Herbert. This analysis indicated the merger could be accretive to Burke & Herbert’s estimated 2024 EPS and estimated 2025 EPS and could be dilutive to Burke & Herbert’s estimated tangible book value per share at closing assumed as of December 31, 2023. Furthermore, the analysis indicated that, pro forma for the merger, each of Burke & Herbert’s tangible common equity to tangible assets ratio, Tier 1 Leverage Ratio, Common Equity Tier 1 Ratio, Tier 1 Capital Ratio and Total Risk-based Capital Ratio at closing assumed as of December 31, 2023 could be lower. For all of the above analysis, the actual results achieved by Burke & Herbert following the merger may vary from the projected results, and the variations may be material.

Burke & Herbert Dividend Discount Model Analysis

KBW performed a dividend discount model analysis of Burke & Herbert to estimate a range for the implied equity value of Burke & Herbert. In this analysis, KBW used financial forecasts and projections relating to the earnings and assets of Burke & Herbert provided by Burke & Herbert management, and KBW assumed discount rates ranging from 9.0% to 13.0%. The range of values was derived by adding (i) the present value of the implied future excess capital available for dividends that Burke & Herbert could generate over the period from December 31, 2023 through December 31, 2028 as a standalone company, and (ii) the present value of Burke & Herbert’s implied terminal value at the end of such period. KBW assumed that Burke & Herbert would maintain a common equity tier 1 ratio of 15.0% and would retain sufficient earnings to maintain that level. In calculating the terminal value of Burke & Herbert, KBW applied a range of 8.0x to 12.0x Burke & Herbert’s estimated 2029 earnings. This dividend discount model analysis resulted in a range of implied values per share of Burke & Herbert common stock of $45.04 to $66.05.

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The dividend discount model analysis is a widely used valuation methodology, but the results of such methodology are highly dependent on the assumptions that must be made, including asset and earnings growth rates, terminal values, and discount rates. The foregoing dividend discount model analysis did not purport to be indicative of the actual values or expected values of Burke & Herbert or the pro forma continuing corporation.

Summit Dividend Discount Model Analysis

KBW performed a dividend discount model analysis of Summit to estimate a range for the implied equity value of Summit. In this analysis, KBW used publicly available consensus “street estimates” of Summit and assumed long-term growth rates for Summit provided by Burke & Herbert management, and KBW assumed discount rates ranging from 10.0% to 13.0%. The range of values was derived by adding (i) the present value of the implied future excess capital available for dividends that Summit could generate over the period from December 31, 2023 through December 31, 2028 as a standalone company, and (ii) the present value of Summit’s implied terminal value at the end of such period. KBW assumed that Summit would maintain a common equity tier 1 ratio of 10.0% and would retain sufficient earnings to maintain that level. In calculating the terminal value of Summit, KBW applied a range of 8.0x to 12.0x Summit’s estimated 2029 earnings. This dividend discount model analysis resulted in a range of implied values per share of Summit common stock of $31.99 to $50.17.

The dividend discount model analysis is a widely used valuation methodology, but the results of such methodology are highly dependent on the assumptions that must be made, including asset and earnings growth rates, terminal values, and discount rates. The foregoing dividend discount model analysis did not purport to be indicative of the actual values or expected values of Summit.

Illustrative Pro Forma Combined Dividend Discount Model Analysis

KBW performed an illustrative dividend discount model analysis of the pro forma continuing corporation. In this analysis, KBW used financial forecasts and projections relating to the earnings and assets of Burke & Herbert provided by Burke & Herbert management, publicly available consensus “street estimates” for Summit, certain adjustments thereto and assumed long-term growth rates for Summit provided by Burke & Herbert management, and pro forma assumptions (including, without limitation, the cost savings expected to result or be derived from the merger, certain purchase accounting and other merger-related adjustments and restructuring charges assumed with respect thereto and assumptions regarding the sale of interest rate hedges of Summit and the redemption of trust preferred securities of Summit) provided by Burke & Herbert management, and KBW assumed discount rates ranging from 10.0% to 13.0%. An illustrative range for the implied equity value of the pro forma continuing corporation was derived by adding (i) the present value of the implied future excess capital available for dividends that the pro forma continuing corporation could generate over the period from December 31, 2023 through December 31, 2028, and (ii) the present value of the pro forma continuing corporation’s implied terminal value at the end of such period, in each case applying the pro forma assumptions. KBW assumed that the pro forma continuing corporation maintains a common equity tier 1 ratio of 10.0% and would retain sufficient earnings to maintain that level. In calculating implied terminal values of the pro forma continuing corporation, KBW applied a range of 8.0x to 12.0x the pro forma continuing corporation’s estimated 2029 earnings. This dividend discount model analysis resulted in an illustrative range of implied values per share of Burke & Herbert common stock of $66.45 to $96.48.

The dividend discount model analysis is a widely used valuation methodology, but the results of such methodology are highly dependent on the assumptions that must be made, including asset and earnings growth rates, terminal values, and discount rates. The foregoing dividend discount model analysis did not purport to be indicative of the actual values or expected values of Burke & Herbert or the pro forma continuing corporation.

Miscellaneous

KBW acted as financial advisor to Burke & Herbert in connection with the proposed merger and did not act as an advisor to or agent of any other person. As part of its investment banking business, KBW is continually engaged in the valuation of bank and bank holding company securities in connection with acquisitions, negotiated underwritings, secondary distributions of listed and unlisted securities, private placements and valuations for various other purposes. As specialists in the securities of banking companies, KBW has experience in, and knowledge of,

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the valuation of banking enterprises. KBW and its affiliates, in the ordinary course of its and their broker-dealer businesses (and further to existing sales and trading relationships between each of Burke & Herbert and Summit and a KBW broker-dealer affiliate), may from time-to-time purchase securities from, and sell securities to Burke & Herbert and Summit. In addition, as a market maker in securities, KBW and its affiliates may from time to time have a long or short position in, and buy or sell, debt or equity securities of Burke & Herbert or Summit for its and their own respective accounts and for the accounts of its and their respective customers and clients.

Pursuant to the KBW engagement agreement, Burke & Herbert has agreed to pay KBW a cash fee equal to 0.80% of the aggregate merger consideration, $500,000 of which became payable to KBW with the rendering of KBW’s opinion and the balance of which is contingent upon the closing of the merger. Burke & Herbert also agreed to indemnify KBW against certain liabilities relating to or arising out of KBW’s engagement or KBW’s role in connection therewith. Other than in connection with the present engagement, in the two years preceding the date of the opinion, KBW did not provide investment banking or financial advisory services to Burke & Herbert. In the two years preceding the date of KBW’s opinion, KBW did not provide investment banking or financial advisory services to Summit. KBW may in the future provide investment banking and financial advisory services to Burke & Herbert or Summit and receive compensation for such services.

Summit’s Reasons for the Merger; Recommendation of Summit’s Board of Directors

After careful consideration, at a meeting held on August 24, 2023, the Summit board of directors determined that the merger agreement and the transactions contemplated thereby are in the best interests of Summit and its shareholders. Accordingly, the Summit board approved and adopted the merger agreement and unanimously recommended that the Summit shareholders vote “FOR” the Summit merger proposal, the Summit compensation proposal, and the Summit adjournment proposal.

In reaching its decision to approve and adopt the merger agreement and recommend that the Summit shareholders vote “FOR” the Summit merger proposal, the Summit board consulted with the senior management of Summit, as well as Summit’s independent financial and legal advisors, and considered a number of factors, including, without limitation, the following factors which are not presented in order of priority:

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The Summit board also considered a number of potential risks and uncertainties associated with the merger agreement and the transactions contemplated thereby, in connection with its deliberations including, without limitation, the following which are not presented in order of priority:

The foregoing discussion of the information and factors considered by the Summit board is not intended to be exhaustive, but rather includes the material factors considered by the Summit board. In reaching its decision to approve and adopt the merger agreement, approve the merger and recommend that Summit shareholders approve the Summit merger proposal, the Summit compensation proposal, and the Summit adjournment proposal, the Summit board did not quantify or assign any relative weights to the factors considered, and individual directors may have given different weights to different factors. The Summit board considered all these factors as a whole, including discussions with and questioning of Summit’s senior management and independent financial and legal advisors, and overall considered the factors to be favorable to, and support, its determination to approve and adopt the merger agreement, approve the merger and recommend that Summit shareholders approve the Summit merger proposal.

This explanation of the Summit board’s reasoning and other information presented in this section is forward-looking in nature and, therefore, should be read in light of the factors discussed under the heading “Cautionary Statement Regarding Forward-Looking Statements.”

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For the reasons set forth above, the Summit board approved and adopted the merger agreement, approved the merger, and unanimously recommends that the Summit shareholders vote “FOR” the Summit merger proposal, the Summit compensation proposal, and the Summit adjournment proposal.

Summit shareholders should be aware that directors and executive officers of Summit may have interests in the merger that are different from, or in addition to, those of other Summit shareholders. See “—Interests of Certain Summit Directors and Executive Officers in the Merger.”

Opinion of Summit’s Financial Advisor

On May 31, 2023, Summit entered into an engagement agreement with D.A. Davidson to render financial advisory and investment banking services to Summit. As part of its engagement, D.A. Davidson agreed to assist Summit in analyzing, structuring, negotiating and, if appropriate, effecting a transaction between Summit and Burke & Herbert. D.A. Davidson also agreed to provide Summit’s board of directors with an opinion as to the fairness, from a financial point of view, of the exchange ratio to the holders of Summit common stock in the proposed merger. Summit engaged D.A. Davidson because D.A. Davidson is a nationally recognized investment banking firm with substantial experience in transactions similar to the merger and is familiar with Summit and its business. As part of its investment banking business, D.A. Davidson is continually engaged in the valuation of financial institutions and their securities in connection with mergers and acquisitions and other corporate transactions.

On August 24, 2023, the Summit board of directors held a meeting to evaluate the proposed merger. At this meeting, D.A. Davidson reviewed the financial aspects of the proposed merger and rendered an opinion to the Summit board that, as such date and based upon and subject to assumptions made, procedures followed, matters considered and limitations on the review undertaken, the exchange ratio was fair, from a financial point of view, to the holders of Summit common stock in the proposed merger.

The full text of D.A. Davidson’s written opinion, dated August 24, 2023, is attached as Annex C to this joint proxy statement/prospectus and is incorporated herein by reference. The description of the opinion set forth herein is qualified in its entirety by reference to the full text of such opinion. Summit’s shareholders are urged to read the opinion in its entirety.

D.A. Davidson’s opinion speaks only as of the date of the opinion and D.A. Davidson undertakes no obligation to revise or update its opinion. The opinion is directed to the Summit board of directors and addresses only the fairness, from a financial point of view, of the exchange ratio to the holders of Summit common stock in the proposed merger. The opinion does not address, and D.A. Davidson does not express a view or opinion with respect to, (i) the underlying business decision of Summit to engage in the merger, (ii) the relative merits or effect of the merger as compared to any alternative business transactions or strategies that may be or may have been available to or contemplated by Summit or the Summit board of directors, or (iii) any legal, regulatory, accounting, tax or similar matters relating to Summit, its shareholders or relating to or arising out of the merger. The opinion does not express a view or opinion as to any terms or other aspects of the merger, except for the exchange ratio. Summit and Burke & Herbert determined the exchange ratio through the negotiation process. The opinion does not express any view as to the amount or nature of the compensation to any of Summit’s or Burke & Herbert’s officers, directors or employees, or any class of such persons, relative to the exchange ratio, or with respect to the fairness of any such compensation. The opinion has been reviewed and approved by D.A. Davidson’s Fairness Opinion Committee in conformity with its policies and procedures established under the requirements of Rule 5150 of the Financial Industry Regulatory Authority.

D.A. Davidson has reviewed the registration statement on Form S-4 of which this joint proxy statement/prospectus is a part and consented to the inclusion of its opinion to the Summit board of directors as Annex C to this joint proxy statement/prospectus and to the references to D.A. Davidson and its opinion contained herein. A copy of the consent of D.A. Davidson is attached as Exhibit 99.4 to the registration statement on Form S-4.

In connection with rendering its opinion, D.A. Davidson reviewed, among other things, the following:

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In arriving at its opinion, D.A. Davidson assumed and relied upon the accuracy and completeness of all information that was publicly available, supplied or otherwise made available to, discussed with or reviewed by or for D.A. Davidson. D.A. Davidson did not independently verify, and did not assume responsibility for independently verifying, such information. D.A. Davidson relied on the assurances of senior management of Summit that they are not aware of any facts or circumstances that would make any of such information, projections or estimates inaccurate or misleading. D.A. Davidson did not undertake an independent evaluation or appraisal of any of the assets or liabilities (contingent or otherwise) of Summit. In addition, D.A. Davidson did not assume any obligation to conduct, nor did D.A. Davidson conduct any physical inspection of the properties or facilities of Summit and has not been provided with any reports of such physical inspections. D.A. Davidson assumed that there has been no material change in Summit’s business, assets, financial condition, results of operations, cash flows, or prospects since the date of the most recent financial statements provided to D.A. Davidson.

With respect to the financial projections and estimates (including information relating to the amounts and timing of merger costs, cost savings, and revenue enhancements) provided to or otherwise reviewed by or for or discussed with us, we have been advised by senior management of Summit and senior management of Burke & Herbert that such projections and other analyses were reasonably prepared on bases reflecting the best currently available estimates and good faith judgments of management of senior management of Summit and senior management of Burke & Herbert as to the future financial performance of Summit and Burke & Herbert and the other matters covered thereby, and that the financial results reflected in such projections and estimates will be realized in the amounts and at the times projected. We do not assume responsibility for and do not express an opinion as to these projections and estimates or the assumptions on which they were based. We have relied on the assurances of senior

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management of Summit that they are not aware of any facts or circumstances that would make any of such information, projections or estimates inaccurate or misleading.

D.A. Davidson did not make an independent evaluation or appraisal of the loan and lease portfolios, classified loans, other real estate owned or any other specific assets, nor has D.A. Davidson assessed the adequacy of the allowance for loan losses of Summit or Burke & Herbert. D.A. Davidson has not reviewed any individual credit files relating to Summit or Burke & Herbert. D.A. Davidson assumed that the respective allowances for loan losses for both Summit and Burke & Herbert are adequate to cover such losses and will be adequate on a pro forma basis for the continuing corporation. D.A. Davidson did not make an independent evaluation of the quality of Summit’s or Burke & Herbert’s deposit base, nor have we independently evaluated potential deposit concentrations or the deposit composition of Summit or Burke & Herbert. D.A. Davidson did not make an independent evaluation of the quality of Summit’s or Burke & Herbert’s investment securities portfolio, nor have we independently evaluated potential concentrations in the investment securities portfolio of Summit or Burke & Herbert.

D.A. Davidson assumed that all representations and warranties contained in the merger agreement and all related agreements are true and correct in all respects material to D.A. Davidson’s analysis, and that the merger will be consummated in accordance with the terms of the merger agreement, without waiver, modification, or amendment of any term, condition or covenant thereof the effect of which would be in any respect material to D.A. Davidson’s analysis. D.A. Davidson has assumed that all material governmental, regulatory or other consents, approvals, and waivers necessary for the consummation of the merger will be obtained without any material adverse effect on Summit or the contemplated benefits of the merger. Further, D.A. Davidson assumed that the executed merger agreement did not differ in any material respect from the draft merger agreement, dated August 23, 2023.

D.A. Davidson assumed in all respects material to its analysis that Summit and Burke & Herbert will remain as going concerns for all periods relevant to its analysis. D.A. Davidson expresses no opinion regarding the liquidation value of Summit and Burke & Herbert or any other entity. D.A. Davidson’s opinion was necessarily based upon information available to D.A. Davidson and economic, market, financial and other conditions as they exist and can be evaluated on the date the fairness opinion letter was delivered to the Summit board of directors.

D.A. Davidson expresses no view as to, and our opinion does not address, the relative merits of the merger as compared to any alternative business transactions or strategies, or whether such alternative transactions or strategies could be achieved or are available. In addition, our opinion does not address any legal, regulatory, tax or accounting matters, as to which we understand that Summit obtained such advice as it deemed necessary from qualified professionals.

D.A. Davidson expresses no opinion as to the actual value of Burke & Herbert common stock when issued in the merger or the prices at which Burke & Herbert common stock will trade following announcement of the merger or at any future time.

D.A. Davidson has not evaluated the solvency or fair value of Summit or Burke & Herbert under any state, federal or other laws relating to bankruptcy, insolvency or similar matters. This opinion is not a solvency opinion and does not in any way address the solvency or financial condition of Summit or Burke & Herbert. D.A. Davidson is not expressing any opinion as to the impact of the merger on the solvency or viability of Summit or Burke & Herbert or the ability of Summit or Burke & Herbert to pay their respective obligations when they come due.

Set forth below is a summary of the material financial analyses performed by D.A. Davidson in connection with rendering its opinion. The summary of the analyses of D.A. Davidson set forth below is not a complete description of the analysis underlying its opinion, and the order in which these analyses are described below is not indicative of any relative weight or importance given to those analyses by D.A. Davidson. The following summaries of financial analyses include information presented in tabular format. You should read these tables together with the full text of the summary financial analyses, as the tables alone are not a complete description of the analyses.

Unless otherwise indicated, the following quantitative information, to the extent it is based on market data, is based on market data as of August 22, 2023, and is not necessarily indicative of market conditions after such date.

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Sensitivity Analysis on Burke & Herbert Stock Price – Merger Consideration (Illustrative Example)

D.A. Davidson analyzed the sensitivity of the value of the merger consideration based on movement in Burke & Herbert’s stock price of +/- 20.0% vs. Burke & Herbert’s closing stock price of $49.31, as of August 22, 2023. Assuming Burke & Herbert’s stock price of $49.31, the merger consideration value was $24.87 per share or $366.3 million. Assuming Burke & Herbert’s stock price increased by 20.0%, the merger consideration value would increase to $29.84 per share or $442.6 million. Conversely, assuming Burke & Herbert’s stock price decreased by 20.0%, the merger consideration value would decrease to $19.89 per share or $292.0 million. Additionally, D.A. Davidson analyzed the sensitivity of the merger consideration value based on Burke & Herbert’s 52-week high stock price, 52-week low stock price and various volume weighted-average prices.

Pro Forma Dividends

D.A. Davidson reviewed Burke & Herbert’s dividend yield over the last twelve months, dividend payout ratio over the last five quarters, dividends per share over last five quarters and dividends per share over the next three quarters using internal company estimates, as discussed with and confirmed by senior management of Burke & Herbert. In addition, D.A. Davidson analyzed the amount of pro forma dividends per share that holders of Summit common stock will receive per current Summit share owned on a quarterly and annual basis using the exchange ratio. The results of this analysis are summarized in the table below.

Stock Price Performance and Volume of Summit and Burke & Herbert

D.A. Davidson reviewed the history of the reported trading prices and volume of Summit common stock and Burke & Herbert common stock and certain stock indices, including the S&P 500 Index, the S&P U.S. BMI Banks Index and the Nasdaq Bank Index. D.A. Davidson compared the stock price performance of Summit or Burke &

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Herbert with the performance of the S&P 500 Index, the S&P U.S. BMI Banks Index and the Nasdaq Bank Index as follows: