Form 424B3 BANNER CORP

On April 30, 2026, Pacific Financial Corporation (“Pacific Financial”) and Banner Corporation (“Banner”) entered into an Agreement and Plan of Merger, which we refer to as the “merger agreement,” under which Pacific Financial will merge with and into Banner, which we refer to as the “merger.” Immediately following the completion of the merger, Bank of the Pacific, the wholly-owned subsidiary of Pacific Financial, will merge with and into Banner Bank, the wholly-owned bank subsidiary of Banner, with Banner Bank continuing as the surviving bank (which we refer to as the “bank merger”).

If the merger is consummated, each issued and outstanding share of Pacific Financial common stock (other than shares held directly by Banner or any holder of Pacific Financial common stock who properly exercises dissenters’ rights) will be converted into the right to receive 0.2633 shares (the “exchange ratio”) of Banner common stock, with cash paid in lieu of fractional shares. A copy of the merger agreement is attached as Appendix A to the accompanying proxy statement/prospectus and is incorporated by reference herein.

Based on the number of outstanding shares of Pacific Financial common stock and Pacific Financial restricted stock unit (“RSU”) awards as of June 12, 2026, Banner expects to issue approximately 2,654,957 shares of its common stock in the merger, excluding the additional shares of Banner common stock that may be issued in the merger to holders of Pacific Financial stock options that properly exercise their stock options in accordance with the merger agreement.

If the merger is consummated, based on the number of issued and outstanding shares of Banner common stock and shares of Pacific Financial common stock and RSU awards on June 12, 2026, we expect that Banner shareholders will own approximately 93%, and current Pacific Financial shareholders will own approximately 7%, of the outstanding shares of common stock of the combined company.

Banner’s common stock is listed on the Nasdaq Global Select Market (“Nasdaq”) under the symbol “BANR.” Pacific Financial’s common stock is quoted on the OTCQX under the symbol “PFLC.” Based on the closing price of Banner common stock as reported by Nasdaq of $66.25 as of April 29, 2026, the trading day immediately preceding the public announcement of the merger, the implied merger consideration that a Pacific Financial shareholder would be entitled to receive for each share of Pacific Financial common stock owned would be $17.44, with an aggregate transaction value of approximately $177 million. Based on the closing price of Banner common stock as reported by Nasdaq of $67.24 as of June 12, 2026, the latest practicable date before the date of the accompanying proxy statement/prospectus, the implied merger consideration that a Pacific Financial shareholder would be entitled to receive for each share of Pacific Financial common stock owned would be $17.70, with an aggregate transaction value of approximately $178.5 million. We urge you to obtain current market quotations of both Banner common stock and Pacific Financial common stock.

We cannot consummate the merger unless we obtain the necessary regulatory approvals and unless the Pacific Financial shareholders approve the merger agreement. Whether or not you plan to participate in the special meeting, please take the time to vote by following the voting instructions included in the enclosed proxy card. Submitting a proxy now will not prevent you from being able to vote electronically during the special meeting. If you do not vote your shares as instructed in the enclosed proxy card, or if you do not instruct your broker how to vote any shares held for you in “street name,” the effect will be a vote against the merger agreement. Your vote is important, regardless of the number of shares that you own.

The date, time and place of the Pacific Financial special meeting are:

The special meeting will be a virtual meeting conducted solely online via live webcast. There is no physical location for the special meeting.

The accompanying proxy statement/prospectus contains a more complete description of the special meeting of Pacific Financial shareholders and the terms of the merger. We urge you to review this entire document carefully. You may also obtain information about Banner from documents that Banner has filed with the Securities and Exchange Commission (the “SEC”).

Pacific Financial’s board of directors recommends that Pacific Financial’s shareholders vote “FOR” the proposal to approve the merger agreement and “FOR” the adjournment proposal.

You should read this entire proxy statement/prospectus carefully because it contains important information about the merger. In particular, you should read carefully the information under the section entitled “Risk Factors” beginning on page 15.

Neither the SEC nor any state securities regulatory body has approved or disapproved of the securities to be issued under the accompanying proxy statement/prospectus or determined if the accompanying proxy statement/prospectus is truthful or complete. Any representation to the contrary is a criminal offense. The securities to be issued in connection with the merger are not savings or deposit accounts or other obligations of any bank or nonbank subsidiary of any of the parties, and they are not insured by the Federal Deposit Insurance Corporation or any other governmental agency.

The accompanying proxy statement/prospectus is dated June 16, 2026, and is first being mailed to Pacific Financial shareholders on or about June 18, 2026.

NOTICE IS HEREBY GIVEN that Pacific Financial Corporation (“Pacific Financial”) will hold a special meeting of its shareholders on Wednesday, August 12, 2026 at 10:00 a.m., Pacific Time, virtually, via live webcast only. The special meeting will be held virtually only and, because there will not be a physical location for the special meeting, you will not be able to attend in person. You can participate in the special meeting by visiting www.virtualshareholdermeeting.com/PFLC2026SM. To participate in the special meeting, registered shareholders will need the control number on their proxy card and all other shareholders will need to follow the instructions that accompanied the proxy statement/prospectus.

The purpose of the special meeting is to consider and vote on the following matters:

Holders of record of Pacific Financial common stock at the close of business on June 11, 2026, are entitled to receive this notice and to vote at the special meeting and any adjournments or postponements thereof. The presence, virtually or by proxy, of a majority of the shares of Pacific Financial common stock entitled to vote is necessary to constitute a quorum for the special meeting. Approval of the merger proposal requires the affirmative vote, virtually or by proxy, of the holders of two-thirds of the outstanding shares of Pacific Financial common stock entitled to vote. Approval of the adjournment proposal requires the affirmative vote of a majority of the shares for which votes are cast at the special meeting, virtually or by proxy. A copy of the merger agreement is attached as Appendix A to the accompanying proxy statement/prospectus, and a summary of the terms of the merger agreement is included in the accompanying proxy statement/prospectus under the heading “Description of the Merger Agreement” beginning on page 53; both are incorporated by reference herein.

Under Washington law, dissenters’ rights are available to Pacific Financial shareholders with respect to the merger if such shareholder takes certain actions and meets certain conditions.

The board of directors of Pacific Financial unanimously recommends that you vote “FOR” the merger proposal and “FOR” the adjournment proposal.

Your vote is important. Whether or not you plan to participate in the special meeting, please act promptly to vote your shares. You may vote your shares by completing, signing and dating a proxy card and returning it in the accompanying postage paid envelope. Please review the instructions for each of your voting options described in the accompanying proxy statement/prospectus. If you participate in the special meeting, you may vote your shares electronically during the special meeting, even if you have previously submitted a proxy in writing. Submitting a proxy will ensure that your shares are represented at the special meeting.

If you are a holder of Pacific Financial stock certificates, we will send you a letter of transmittal separately on a later date with instructions informing you how to send in your stock certificates to the exchange agent to receive your portion of the merger consideration. Please do not send in your stock certificates at this time.

If you have any questions regarding the accompanying proxy statement/prospectus, you may contact Pacific Financial’s proxy solicitor D.F. King at:

This proxy statement/prospectus incorporates important business and financial information about Banner from documents filed with the SEC that are not included in or delivered with this proxy statement/prospectus. For a listing of the documents incorporated by reference into this proxy statement/prospectus, please see the section entitled “Where You Can Find More Information.” You can obtain any of the documents filed with or furnished to the SEC by Banner at no cost from the SEC’s website at http://www.sec.gov. You may also request copies of these documents, including documents incorporated by reference in this proxy statement/prospectus, at no cost by requesting them in writing or by telephone at the following addresses and telephone numbers:

The section of this proxy statement/prospectus entitled “Where You Can Find More Information” has additional information about obtaining copies of documents that Banner have filed with the SEC.

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 special meeting. This means that Pacific Financial shareholders requesting documents must do so by August 4, 2026 to receive them before the Pacific Financial special meeting.

Pacific Financial does not have a class of securities registered under Section 12 of the Securities Exchange Act of 1934 (the “Exchange Act”), is not subject to the reporting requirements of Section 13(a) or 15(d) of the Exchange Act, and accordingly does not file documents or reports with the SEC.

If you have questions concerning the merger or this proxy statement/prospectus or need help voting your shares, would like copies of this proxy statement/prospectus, or would like copies of Pacific Financial’s historical consolidated financial statements, articles of incorporation or bylaws, please contact:

This document, which forms part of a registration statement on Form S-4 filed with the SEC by Banner (File No. 333-296472), constitutes a prospectus of Banner under Section 5 of the Securities Act of 1933, as amended, with respect to the shares of common stock, par value $0.01 per share, of Banner, which we refer to as “Banner common stock,” to be issued pursuant to the Agreement and Plan of Merger, dated as of April 30, 2026, by and between Banner and Pacific Financial, as it may be amended from time to time, which we refer to as the “merger agreement.” This document also constitutes a proxy statement of Pacific Financial and a notice of meeting with respect to the special meeting at which Pacific Financial shareholders will be asked to consider and vote upon the approval of the merger agreement.

Banner has supplied all information contained in or incorporated by reference into this proxy statement/prospectus relating to Banner, and Pacific Financial has supplied all information contained in this proxy statement/prospectus relating to Pacific Financial.

You should rely only on the information contained in, or incorporated by reference into, this document. 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 June 16, 2026, 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 document. The mailing of this document to Pacific Financial shareholders or the issuance by Banner of shares of Banner common stock pursuant to the merger agreement will create any implication to the contrary.

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.

The following questions and answers are intended to briefly address some commonly asked questions regarding the merger, the merger agreement, and the virtual Pacific Financial Corporation (“Pacific Financial”) special meeting. We urge you to read carefully the remainder of this proxy statement/prospectus because the information in this section may not provide all the information that might be important to you in determining how to vote. Additional important information is also contained in the appendices to, and the documents incorporated by reference in, this document. See “Where You Can Find More Information.”

In addition to general investment risks and the other information contained in or incorporated by reference into this proxy statement/prospectus, including the matters addressed under the section “Special Note Regarding Forward-Looking Statements,” you should carefully consider the following risk factors in deciding how to vote for the proposals presented in this proxy statement/prospectus. You should also consider the other information in this proxy statement/prospectus and the other documents incorporated by reference into this proxy statement/prospectus. See “References to Additional Information” in the forepart of this proxy statement/prospectus and the section of this proxy statement/prospectus entitled “Where You Can Find More Information.”

The exchange ratio determining the number of shares of Banner common stock to be issued in the merger in exchange for each share of Pacific Financial common stock is fixed. The exchange ratio will not adjust based on the trading price of Banner common stock, and the market value of those shares may vary from the closing price of Banner common stock on the date the merger was announced, on the date that this document was mailed to Pacific Financial shareholders, on the date of the special meeting, on the date the merger is consummated and thereafter. Any change in the market price of Banner common stock prior to consummation of the merger will affect the amount of and the market value of the merger consideration that Pacific Financial shareholders will receive upon consummation of the merger. Accordingly, at the time of the special meeting, shareholders will not know or be able to calculate with certainty the market value of the Banner common stock to be issued to Pacific Financial shareholders upon consummation of the merger. Stock price changes may result from a variety of factors, including general market and economic conditions, changes in business, operations and prospects, and regulatory considerations. Many of these factors are beyond Banner’s or Pacific Financial’s control. You should obtain current market quotations of both Banner common stock and Pacific Financial common stock before you vote.

Upon consummation of the merger, holders of Pacific Financial common stock will become holders of Banner common stock. Banner’s business differs in important respects from that of Pacific Financial. Accordingly, the results of operations of the combined company and the market price of Banner common stock after the consummation of the merger may be affected by factors different from those currently affecting the independent results of operations of each of Banner and Pacific Financial. For a discussion of Banner’s business and markets and some important factors to consider in connection with its business, please see the documents incorporated by reference in this proxy statement/prospectus and referred to under “Where You Can Find More Information.”

Pursuant to the merger agreement and based on the number of outstanding shares of Pacific Financial common stock and Pacific Financial RSU awards as of June 11, 2026, Banner expects to issue approximately 2,654,957 shares of its common stock in the merger, excluding the additional shares of Banner common stock that may be issued in the merger to holders of Pacific Financial stock options that properly exercise their stock options in accordance with the merger agreement. The dilution caused by the issuance of a large number of new shares of Banner common stock may result in fluctuations in the market price of Banner common stock, including a potential stock price decrease.

Pacific Financial shareholders currently have the right to vote in the election of the Pacific Financial Board and on other matters requiring shareholder approval under Washington law and Pacific Financial’s articles of incorporation and bylaws. Upon the consummation of the merger, each Pacific Financial shareholder will become a shareholder of Banner with a percentage ownership of Banner that is smaller than such shareholder’s current percentage ownership of Pacific Financial.

Based on the number of outstanding shares of Pacific Financial common stock and Pacific Financial RSU awards as of June 11, 2026, Banner expects to issue approximately 2,654,957 shares of its common stock in the merger,

excluding the additional shares of Banner common stock that may be issued in the merger to holders of Pacific Financial stock options that properly exercise their stock options in accordance with the merger agreement. After the merger is consummated, if Banner issues 2,654,957 shares in the merger, we expect that current Banner shareholders will own approximately 93% of the outstanding shares of common stock of the combined company, and current Pacific Financial shareholders will own approximately 7% of the outstanding shares of common stock of the combined company (without giving effect to any Banner common stock held by Pacific Financial shareholders prior to the merger). Because of this, current Pacific Financial shareholders, as a group, will have significantly less influence on the board of directors, management and policies of Banner (as the combined company following the merger) than they now have on the board of directors, management and policies of Pacific Financial.

Pacific Financial common stock is quoted on the OTCQX market maintained by OTC Market Groups, Inc., under the symbol “PFLC.” Pacific Financial’s common stock has traded in limited trading volumes compared to active exchange-listed stocks and its trading history may not be representative of the prices at which Pacific Financial common stock would trade on a more active market. Over-the-counter market quotations reflect inter-dealer pricing without retail markup, markdown or commissions, and may not reflect actual transactions. As a result, it may be more difficult for Pacific Financial shareholders to determine how the value of the per share merger consideration compares to the market price of Pacific Financial common stock. Pacific Financial shareholders are encouraged to review the discussion of the Pacific Financial Board’s valuation analysis and the opinion of Pacific Financial’s financial advisor described in “The Merger—Opinion of Pacific Financial’s financial advisor” in evaluating the fairness of the per share merger consideration.

Banner and Pacific Financial have operated and, until the consummation of the merger, will continue to operate, independently. The success of the merger, including anticipated benefits and cost savings, will depend on, among other things, Banner’s ability to combine the businesses of Banner and Pacific Financial in a manner that permits growth opportunities, including, among other things, enhanced revenues and revenue synergies, an expanded market reach and operating efficiencies, and does not materially disrupt the existing customer relationships of Banner or Pacific Financial nor result in decreased revenues due to loss of customers. If Banner is 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. Failure to achieve these anticipated benefits could result in increased costs, decreases in the amount of expected revenues and diversion of management’s time and energy and could have an adverse effect on the surviving corporation’s business, financial condition, operating results, prospects and stock price.

While individuals employed by Pacific Financial or Bank of the Pacific immediately prior to the effective time will automatically become employees of Banner or Banner Bank following the merger, certain employees may not be retained by Banner after the merger. In addition, certain employees that Banner wishes to retain may elect to terminate their employment as a result of the merger, which could delay or disrupt the integration process. It is possible that the integration process could result in the disruption of Banner’s or Pacific Financial’s ongoing businesses or cause differences in standards, controls, procedures and policies that adversely affect the ability of Banner or Pacific Financial to maintain relationships with customers and employees or to achieve the anticipated benefits and cost savings of the merger.

Before the transactions contemplated in the merger agreement can be consummated, various approvals must be obtained from the banking regulators and other governmental authorities. In deciding whether to grant regulatory clearances, the relevant governmental entities will consider a variety of factors, including the regulatory standing of each of the parties. An adverse condition or development in either party’s regulatory standing or other factors could result in an inability to obtain one or more of the required regulatory approvals, or delay their receipt. The terms and conditions of the approvals that are granted may impose requirements, limitations or costs, or may place restrictions on the conduct of the combined company’s business.

Banner and Pacific Financial believe that the merger should not raise significant regulatory concerns, and that the parties will be able to obtain all requisite regulatory approvals in a timely manner. Despite the parties’ commitments to use their reasonable best efforts to comply with conditions imposed by regulatory entities, under the terms of the merger agreement, Banner and Pacific Financial will not be required to consummate the merger if any such approvals would contain or result in or would reasonably be expected to result in, the imposition of a “Burdensome Condition” on Banner. There can be no assurance that regulators will not impose conditions, terms, obligations or restrictions, or that such conditions, terms, obligations or restrictions will not have the effect of delaying the consummation of the merger, imposing additional material costs on or materially limiting the revenues of the combined company following the merger or otherwise reduce the anticipated benefits of the merger if the merger were consummated successfully within the expected timeframe. In addition, neither Banner nor Pacific Financial can provide assurance that any such conditions, terms, obligations or restrictions will not result in the delay or abandonment of the merger. The consummation of the merger is further conditioned on the absence of certain orders, injunctions or decrees by any court or regulatory agency of competent jurisdiction that would prohibit or make illegal the consummation of the merger.

The merger agreement is subject to a number of conditions which must be fulfilled in order to consummate the merger. Those conditions include, among other things: approval of the merger agreement by Pacific Financial shareholders; receipt of certain requisite regulatory approvals; absence of orders prohibiting consummation of the merger; effectiveness of the registration statement of which this proxy statement/prospectus is a part; listing of Banner common stock on Nasdaq; the accuracy of the representations and warranties by both parties set forth in the merger agreement; the performance by both parties of their covenants and agreements as set forth in the merger agreement; and the receipt by both parties of legal opinions from their respective tax counsels. In addition, it is a condition to Banner’s obligations under the merger agreement that Pacific Financial’s adjusted equity (which excludes accumulated other comprehensive loss (or gain), intangible assets and merger costs of Pacific Financial) will be equal to or greater than $124,269,000, calculated 10 business days before closing and certified by Pacific Financial’s chief financial officer, and that holders of less than 10% of Pacific Financial shares of common stock have exercised dissenters’ rights. These conditions to the closing of the merger may not be fulfilled in a timely manner or at all, and, accordingly, the merger may not be consummated. In addition, the parties can mutually decide to terminate the merger agreement at any time, before or after receipt of Pacific Financial shareholder approval, or Banner or Pacific Financial may elect to terminate the merger agreement in certain other circumstances.

If the merger is not consummated for any reason, including as a result of Pacific Financial’s shareholders failing to approve the merger proposal or the failure of the parties to satisfy any other condition of the merger agreement, the ongoing business of Pacific Financial may be adversely impacted and, without realizing any of the anticipated benefits of completing the merger, Pacific Financial would be subject to a number of risks, including the following:

If the merger agreement is terminated and the Pacific Financial Board seeks another merger or business combination, Pacific Financial shareholders cannot be certain that Pacific Financial will be able to find a party willing to offer equivalent or more attractive consideration than the consideration Banner has agreed to provide in the merger, or that such other merger or business combination will be consummated. Additionally, if the merger agreement is terminated under certain circumstances, Pacific Financial may be required to pay a termination fee to Banner of $6.3 million.

Uncertainty about the effect of the merger on employees and customers may have an adverse effect on Pacific Financial and, consequently, on Banner if the merger is completed. These uncertainties may impair Pacific Financial’s ability to attract, retain and motivate key personnel until the merger is consummated, and could cause customers and others that deal with Pacific Financial to seek to change existing business relationships with Pacific Financial. Retention of certain employees may be challenging during the pendency of the merger, as certain employees may experience uncertainty about their future roles. If key employees depart because of issues relating to the uncertainty and difficulty of integration or a desire not to remain with the business, Banner’s business following the merger could be negatively impacted. In addition, the merger agreement restricts Pacific Financial from making certain transactions and taking other specified actions without the consent of Banner until the merger occurs. These restrictions may prevent Pacific Financial from pursuing attractive business opportunities that may arise prior to the consummation of the merger.

The interests of some of the directors and executive officers of Pacific Financial may be different from those of Pacific Financial’s shareholders, and directors and officers of Pacific Financial may be participants in arrangements that are different from, or are in addition to, those of Pacific Financial’s shareholders. The members of the Pacific Financial Board knew about these additional interests and considered them among other matters, when making its decision to approve the merger agreement, and in recommending that holders of Pacific Financial common stock vote in favor of approving the merger agreement. Such interests include, among others:

These interests are more fully described in this proxy statement/prospectus under the heading “The Merger—Interests of certain persons in the merger.”

The merger agreement contains provisions that may discourage a third party from submitting an acquisition proposal to Pacific Financial that might result in greater value to Pacific Financial’s shareholders than the proposed merger with Banner, or that may result in a potential competing acquiror proposing to pay a lower per share price to acquire Pacific Financial than it might otherwise have proposed to pay absent such provisions. These provisions include a general prohibition on Pacific Financial from soliciting, or, subject to certain exceptions relating to the exercise of fiduciary duties by the Pacific Financial Board, entering into discussions with any third party regarding any acquisition proposal or offers for competing transactions. In addition, Pacific Financial may be required to pay Banner a termination fee of $6.3 million upon termination of the merger agreement in certain circumstances involving acquisition proposals for competing transactions. See “Description of the Merger Agreement—Termination” and “Description of the Merger Agreement—Termination fee.”

Pacific Financial obtained an opinion from its financial advisor, Piper Sandler, to the effect that the per share merger consideration to be received in the merger pursuant to the merger agreement was fair, from a financial point of view, to the holders of Pacific Financial common stock, as of April 30, 2026. Pacific Financial has not obtained an updated opinion from its financial advisor as of the date of this proxy statement/prospectus. Changes in the operations

and prospects of Banner or Pacific Financial, general market and economic conditions and other factors that may be beyond the control of Banner or Pacific Financial, may significantly alter the value of Pacific Financial, the price of the Banner common stock to be issued to Pacific Financial shareholders pursuant to the merger agreement or the price of Pacific Financial common stock by the time the merger is consummated. The opinion of Pacific Financial’s financial advisor does not speak as of the time the merger will be consummated, or as of any date other than the date of such opinion. Because Pacific Financial currently does not anticipate asking its financial advisor to update its opinion, the opinion will not address the fairness of the per share merger consideration from a financial point of view, to the holders of Pacific Financial common stock, at the time the merger is consummated.

Each of Banner and Pacific Financial has incurred and expects that it will incur significant, non-recurring costs in connection with consummating the merger. In addition, Banner will incur integration costs, some of which may not be anticipated, following the consummation of the merger as Banner integrates the businesses of the two companies, including facilities and systems consolidation costs and employment-related costs, all of which may affect the total amount or timing of Banner’s integration costs. 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. Banner and Pacific Financial may also incur additional costs to retain key employees or in connection with severance. Banner and Pacific Financial will also incur significant legal, financial advisor, accounting, banking and consulting fees, fees relating to regulatory filings and notices, regulatory filing fees, printing and mailing fees, and other costs associated with the merger.

Upon consummation of the merger, Pacific Financial shareholders will become Banner shareholders. While their rights as shareholders will continue to be governed by the WBCA, their rights will also become governed by Banner’s articles of incorporation and bylaws. The rights associated with Pacific Financial common stock are different from the rights associated with Banner common stock. Please see “Comparison of Rights of Banner Shareholders and Pacific Financial Shareholders” for a discussion of the different rights associated with Banner common stock.

It is possible that, in connection with the merger, shareholders may file demands or putative class action lawsuits against Banner or Pacific Financial (or their respective boards of directors). Among other remedies, these shareholders could seek financial damages or to enjoin the merger. The outcome of any such litigation is uncertain. Additionally, one of the conditions to the closing of the merger is that there must be no order, injunction or decree issued by any court or agency of competent jurisdiction or other legal restraint or prohibition preventing the consummation of the merger or any of the other transactions contemplated by the merger agreement and there must be no order, injunction or decree that prohibits or makes illegal consummation of the merger. If a dismissal is not granted or a settlement is not reached and any plaintiff were successful in obtaining an injunction prohibiting Banner or Pacific Financial from completing the 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 Banner or Pacific Financial, including any cost associated with the indemnification of directors and officers of each company. The defense or settlement of any lawsuit or claim that remains unresolved at the time the merger is consummated may adversely affect the combined company’s business, financial condition, results of operations and cash flows and the market price of the combined company.

Banner and Pacific Financial have not sought, and will not seek, any ruling from the Internal Revenue Service regarding any matters relating to the transactions, and as a result, there can be no assurance that the IRS would not assert that the merger does not qualify as a “reorganization” within the meaning of Section 368(a) of the Internal Revenue Code, or that a court would not sustain such a position. If the merger were to fail to qualify as a reorganization within the meaning of Section 368(a) of the Internal Revenue Code, then each holder of Pacific Financial common stock that expected the tax-deferred reorganization rules of IRC Section 368(a) to apply, generally would recognize a gain or loss,

as applicable, equal to the difference between such holder’s adjusted tax basis in each share of Pacific Financial common stock surrendered and the sum of the fair value of Banner common stock received in exchange for that share upon consummation of the merger. Because Pacific Financial shareholders will not receive cash in exchange for their shares of Pacific Financial common stock, they may need to use cash from other sources or may be required to sell their Banner common stock received in the merger to satisfy the resulting tax liability. See “The Merger—Material U.S. federal income tax consequences of the merger.”

You should read and consider the risk factors specific to Banner’s business that will also affect the combined company after the merger. These risks are described in the sections entitled “Risk Factors” in Banner’s Annual Report on Form 10-K for the year ended December 31, 2025, and in other documents incorporated by reference into this proxy statement/prospectus. Please see the section entitled “Where You Can Find More Information” of this proxy statement/prospectus for the location of information incorporated by reference into this proxy statement/prospectus.

This proxy statement/prospectus contains “forward-looking statements” within the meaning of the safe harbor provisions of the U.S. Private Securities Litigation Reform Act of 1995. Forward-looking statements include, without limitation, statements concerning plans, estimates, calculations, forecasts and projections with respect to the anticipated future performance of Banner and Pacific Financial and certain plans, expectations, goals, projections and benefits relating to the proposed merger between Banner and Pacific Financial, all of which are subject to numerous assumptions, risks and uncertainties. These statements are often, but not always, identified by words such as “may,” “might,” “should,” “could,” “predict,” “potential,” “believe,” “expect,” “continue,” “will,” “anticipate,” “seek,” “estimate,” “intend,” “plan,” “projection,” “would,” “annualized,” “target” and “outlook,” or the negative version of those words or other comparable words of a future or forward-looking nature.

Examples of forward-looking statements include, among others, statements Banner and Pacific Financial make regarding the ability of Banner and Pacific Financial to consummate the transactions contemplated by the merger agreement, including the parties’ ability to satisfy the conditions to the consummation of the merger, statements about the expected timing for completing the merger, the potential effects of the proposed merger on both Banner and Pacific Financial, the possibility of any termination of the merger agreement, projected growth, anticipated future financial performance, financial condition, or credit quality, Banner’s and Pacific Financial’s respective managements’ long-term performance goals and the future prospects of the combined company.

Forward-looking statements are not historical facts but instead express only Banner’s or Pacific Financial’s management’s beliefs regarding future results or events, many of which, by their nature, are inherently uncertain and outside of management’s control. It is possible that actual results and outcomes may differ, possibly materially, from the anticipated results or outcomes indicated in these forward-looking statements. In addition to factors disclosed in reports filed by Banner with the SEC, risks and uncertainties for Banner, Pacific Financial and the combined company that may cause actual results or outcomes to differ materially from those anticipated include, but are not limited to: (1) the business of Pacific Financial may not be integrated with Banner’s business successfully or such integration may be more difficult, time-consuming or costly than expected; (2) any of the anticipated benefits of the proposed merger may not be realized or may not be realized within the expected time period; (3) customer and employee relationships and business operations may be disrupted by the merger or the announcement of the merger, and the parties may be challenged in retaining key relationships both during the pendency of the merger and following the completion of the merger if it occurs; (4) the parties may not meet expectations regarding the timing of the proposed merger; (5) required regulatory approvals or the approval of Pacific Financial shareholders may not be obtained or such approvals may be more difficult, time-consuming or costly than expected; (6) there may be challenges in satisfying the other conditions to completion of the merger or the merger may fail to close for any other reason; (7) management’s attention may be diverted from ongoing business operations and opportunities due to the proposed merger; and (8) there may be potential negative impacts caused by the dilution resulting from Banner’s issuance of shares of Banner common stock in connection with the merger. Further information regarding Banner, Pacific Financial and factors which could affect the forward-looking statements contained herein can be found in the section entitled “Risk Factors.”

Also, please refer to Banner’s Annual Report on Form 10-K for the year ended December 31, 2025 filed with the SEC on February 25, 2026, as well as Banner’s other filings with the SEC, for a more detailed discussion of risks, uncertainties and factors that could cause actual results to differ from those discussed in the forward-looking statements. Banner’s filings with the SEC are incorporated by reference into this proxy statement/prospectus as described in the section entitled “Where You Can Find More Information.”

Any forward-looking statement included in this proxy statement/prospectus is based only on information available to management and speaks only as of the date of this proxy statement/prospectus. Unless required by law, neither Banner nor Pacific Financial undertakes any obligation to publicly update any forward-looking statement, whether written or oral, that may be made from time to time, whether as a result of new information, future developments or otherwise.

Pacific Financial shareholders are receiving this proxy statement/prospectus because, at the close of business on June 11, 2026, the record date for the special meeting of Pacific Financial’s Shareholders to be held at 10:00 a.m. Pacific Time on Wednesday, August 12, 2026, they owned shares of the common stock of Pacific Financial, and the Pacific Financial Board is soliciting proxies for the matters to be voted on at this special meeting, as described in more detail below. The special meeting can be accessed virtually only, via live webcast.

To participate in the special meeting, registered shareholders will need the control number on their proxy card and all other shareholders will need to follow the instructions that accompanied their proxy statement/prospectus.

Pacific Financial began to mail copies of this proxy statement/prospectus to holders of Pacific Financial common stock on June 18, 2026, which included a proxy card for use at the special meeting and at any adjournment(s) of the special meeting.

At the special meeting, the Pacific Financial Board will ask you to vote upon the following proposals:

When you sign the enclosed proxy card or otherwise vote pursuant to the instructions set forth on the proxy card, you appoint the proxy holder as your representative at the special meeting. The proxy holder will vote your shares as you have instructed in the proxy card, thereby ensuring that your shares will be voted whether or not you participate in the special meeting. Even if you plan to participate in the special meeting, we ask that you instruct the proxies how to vote your shares in advance of the special meeting just in case your plans change.

If you have not already done so, please complete, date and sign the accompanying proxy card and return it promptly in the enclosed, postage paid envelope or otherwise vote pursuant to the instructions set forth on the proxy card. If you do not vote your shares as instructed on the proxy card, or if you do not participate in and cast your vote at the special meeting, the effect will be a vote against the merger agreement.

The record date for the special meeting is June 11, 2026. Pacific Financial’s shareholders of record as of the close of business on that day will receive notice of and will be entitled to vote at the special meeting. As of the record date, there were 10,025,137 shares of Pacific Financial common stock outstanding and entitled to vote at the special meeting. The outstanding shares are held by approximately 712 holders of record.

The presence, virtually or by proxy, of a majority of the shares of Pacific Financial common stock entitled to vote on the merger agreement is necessary to constitute a quorum for the special meeting. Each share of Pacific Financial common stock outstanding on the record date entitles its holder to one vote on the matters being brought before the special meeting.

To determine the presence of a quorum for the special meeting, Pacific Financial will also count as present the shares of Pacific Financial common stock present virtually at the special meeting but not voting, and the shares of Pacific Financial common stock for which Pacific Financial has received proxies but with respect to which the holders of such shares have voted “Abstain” or signed without providing instructions. Broker non-votes also are counted as present for the purposes of determining quorum. Based on the number of shares of Pacific Financial common stock outstanding as of the record date, at least 5,012,569 shares of Pacific Financial common stock must be present at the special meeting, whether virtually or by proxy, to constitute a quorum.

Approval of the merger proposal requires the affirmative vote, virtually or by proxy, of the holders of two-thirds of the outstanding shares of Pacific Financial common stock. Abstentions, shares not voted and broker non-votes will have the same effect as a vote against the merger proposal. Approval of the adjournment proposal requires the affirmative vote of a majority of the shares for which votes are cast at the special meeting, virtually or by proxy. Abstentions, shares not voted and broker non-votes will have no effect on the adjournment proposal.

As of the record date for the special meeting, Pacific Financial’s directors and executive officers owned, in the aggregate, a total of 1,235,877 shares, or approximately 12.3% of the outstanding shares, of Pacific Financial common

stock. These individuals, as well as a former Pacific Financial director who retired on April 23, 2026, have entered into a voting and support agreement with Banner and Pacific Financial under which they have agreed that they will vote their shares of Pacific Financial common stock in favor of the merger agreement. The voting and support agreement covers 1,269,358 shares, or approximately 12.7% of Pacific Financial’s outstanding shares of common stock as of the record date for the special meeting.

For more information regarding the voting and support agreement, see “Description of the Merger Agreement—Voting and Support Agreement” beginning on page 54. For more information regarding the interests of Pacific Financial’s directors and executive officers in the merger agreement and the transactions contemplated therein, see “The Merger—Interests of certain persons in the merger” beginning on page 47 and “Beneficial Ownership of Pacific Financial Common Stock by Management and Principal Shareholders of Pacific Financial” beginning on page 68.

Under Washington law, Pacific Financial shareholders are entitled to assert dissenters’ rights with respect to the merger proposal. These dissenters’ rights are conditioned on strict compliance with the requirements of Subchapter 13 of the WBCA. Please see “The Merger—Pacific Financial shareholder dissenters’ rights,” beginning on page 49, and the full text of Subchapter 13 of the WBCA, which is reproduced in full in Appendix C to this proxy statement/prospectus, for additional information.

After you have carefully read and considered the information contained in this proxy statement/prospectus, please vote by a method described on your proxy card or voting instruction form. If you properly complete and timely submit your proxy, your shares will be voted as you have directed. You may vote for, against or abstain with respect to each matter brought before the special meeting. If you are the record holder of your shares and submit your proxy without specifying a voting instruction, your shares will be voted as the Pacific Financial Board recommends and will be voted “FOR” the merger proposal and “FOR” the adjournment proposal. If you do not vote your shares as instructed on the proxy card, or if you do not participate in and cast your vote at the special meeting, the effect will be a vote against the merger agreement. Although you may vote by mail, we ask that you vote instead by Internet or telephone. You may vote by telephone by calling the toll-free number specified on your proxy card or vote by Internet by accessing the website specified on your proxy card and by following the preprinted instructions on the proxy card. The giving of a proxy by either of these means will not affect your right to vote virtually if you decide to participate in the special meeting.

You should not send any stock certificates with your proxy card. If the merger is approved, you will receive instructions for exchanging your stock certificates after the merger has been consummated.

If you hold shares in “street name” with a bank, broker or other fiduciary, you will receive voting instructions from the holder of record of your shares. Under the rules of various national and regional securities exchanges, brokers, banks and other fiduciaries may generally vote your shares on routine matters, such as the ratification of an independent registered public accounting firm, even if you provide no instructions, but may not vote on non-routine matters, such as the matters being brought before the special meeting, unless you provide voting instructions. Shares for which a broker does not have the authority to vote are recorded as “broker non-votes” and are not counted in the vote by shareholders. As a result, any broker non-votes will have the practical effect of a vote against the merger proposal but will not affect the adjournment proposal.

If your shares are registered in the name of your bank, broker or other fiduciary, you are the “beneficial owner” of those shares, and those shares are considered as held in “street name.” If you are a beneficial owner of shares registered in the name or your bank, broker or other fiduciary, you should have received a proxy card and voting instructions with these proxy materials from that organization, rather than directly from Banner or Equiniti. Please follow the instructions on the proxy card provided by your bank, broker or other fiduciary to complete and mail the proxy card to ensure that your vote is counted. You may also be eligible to vote your shares held in “street name” electronically over the Internet or by telephone. A large number of banks and brokerage firms offer Internet and telephone voting. If your bank, broker or other fiduciary does not offer Internet or telephone voting, please complete and return your proxy card pursuant to the instructions on the proxy card provided by your bank, broker or other fiduciary.

To participate in the special meeting, registered shareholders will need the control number on their proxy card and all other shareholders will need to follow the instructions that accompanied their proxy statement/prospectus.

If you have any questions about the merger or how to submit your proxy card, or if you need additional copies of this proxy statement/prospectus, please contact Pacific Financial’s Corporate Secretary, 1216 Skyview Dr., Aberdeen, Washington, 98520 or by calling (360) 537-4052, or D.F. King, Pacific Financial’s proxy solicitor, by calling toll-free at (866) 342-4884, or for banks and brokers, collect at (646) 845-0147, or by email at [email protected].

You may revoke your proxy at any time before the vote is taken at the special meeting. To revoke your proxy, you must either advise the Corporate Secretary of Pacific Financial in writing before your Pacific Financial common stock has been voted at the special meeting, deliver a later dated proxy, granting a subsequent proxy by telephone or through the Internet, or participate in the special meeting and vote your shares electronically during the special meeting. Attendance at the special meeting will not in itself constitute revocation of your proxy.

All written notices of revocation and other communication with respect to the revocation of proxies should be addressed to: Pacific Financial Corporation, Attn: Corporate Secretary, 1216 Skyview Dr., Aberdeen, Washington, 98520. If you hold your shares in the name of a broker, bank or other fiduciary and desire to revoke your proxy, you will need to contact your broker, bank or other fiduciary to revoke your proxy.

Pacific Financial will pay the costs associated with the solicitation of proxies for the special meeting. Pacific Financial will reimburse brokerage firms and other custodians, nominees and fiduciaries for reasonable expenses incurred by them in sending proxy materials to the beneficial owners of Pacific Financial common stock. In addition to the solicitation of proxies by mail, directors, officers and employees of Pacific Financial may solicit proxies personally or by telephone. None of these persons will receive additional compensation for these activities.

On behalf of the Pacific Financial Board, Pacific Financial has engaged D.F. King, a proxy solicitation firm, to solicit proxies for the special meeting. D.F. King will be paid a fixed fee of approximately $18,000, and be reimbursed out-of-pocket expenses for its services. Pacific Financial has also agreed to indemnify D.F. King and its affiliates against certain claims, liabilities, losses, damages and expenses.

At the special meeting, shareholders of Pacific Financial will be asked to approve the merger agreement, pursuant to which Pacific Financial will merge with and into Banner. Shareholders of Pacific Financial should read this proxy statement/prospectus carefully and in its entirety, including the appendices, for more detailed information concerning the merger agreement and the transactions contemplated therein. A copy of the merger agreement is attached to this proxy statement/prospectus as Appendix A.

For the reasons discussed in this proxy statement/prospectus, the Pacific Financial Board unanimously determined that the merger agreement and the transactions contemplated therein are in the best interests of Pacific Financial and its shareholders, and unanimously approved the merger agreement. The Pacific Financial Board unanimously recommends that Pacific Financial shareholders vote “FOR” the merger proposal.

If, at the special meeting, the number of shares of Pacific Financial common stock cast in favor of the merger agreement is insufficient to approve the merger proposal, Pacific Financial intends to move to adjourn the special meeting in order to enable the Pacific Financial Board to solicit additional proxies for approval of the merger proposal. In this proposal, Pacific Financial is asking its shareholders to authorize the holder of any proxy solicited by the Pacific Financial Board, on a discretionary basis, to vote in favor of adjourning the special meeting to another time and place for the purpose of soliciting additional proxies.

This section of the proxy statement/prospectus describes material aspects of the merger. While Banner and Pacific Financial believe that the description covers the material terms of the merger and the related transactions, this summary may not contain all of the information that is important to you. You should carefully read this entire proxy statement/prospectus, the attached Appendices and the other documents to which this proxy statement/prospectus refers for a more complete understanding of the merger. The merger agreement attached hereto as Appendix A, not this summary, is the legal document which governs the merger.

The Pacific Financial Board is using this proxy statement/prospectus to solicit proxies from the holders of Pacific Financial common stock for use at the special meeting of shareholders, at which Pacific Financial shareholders as of the record date will be asked to approve the merger agreement. When the merger is consummated, Pacific Financial will merge with and into Banner and will cease to exist. The merger is anticipated to be consummated in the third quarter of 2026. Immediately following the consummation of the merger, Banner will merge Bank of the Pacific with and into Banner Bank, with Banner Bank as the surviving bank. At such time, Bank of the Pacific’s banking offices will become banking offices of Banner Bank.

If the merger is consummated, each share of Pacific Financial common stock issued and outstanding immediately prior to the effective time (other than shares held directly by Banner or any holder of Pacific Financial common stock who properly exercises dissenters’ rights) will be converted into the right to receive 0.2633 shares of Banner common stock, with cash paid in lieu of fractional shares. The amount of cash paid in lieu of fractional shares will be based on the “Banner Closing Stock Price,” which is the average closing price per share of Banner common stock as reported on the Nasdaq Global Select Market for the 15 consecutive trading days immediately preceding the closing date.

If any holder of a Pacific Financial stock option that may by its terms be exercised provides a notice of exercise to Pacific Financial on or before the 30th calendar day prior to the effective time (such date, the “Option Exercise Notice Deadline”), Pacific Financial will issue shares of Pacific Financial common stock upon proper exercise of the Pacific Financial stock option in accordance with the terms of the such stock option and relevant Pacific Financial stock plan. Each share of Pacific Financial Common Stock received upon proper exercise of a Pacific Financial stock option prior to the Option Exercise Notice Deadline will be treated in the merger in the same manner as other outstanding shares of Pacific Financial common stock at the effective time. However, no exercise of a Pacific Financial stock option will be permitted if an option holder fails to provide notice of exercise to Pacific Financial by the Option Exercise Notice Deadline.

At the effective time, each Pacific Financial stock option that is outstanding as of immediately prior to the effective time will fully vest and will be cancelled and converted into the right to receive a cash payment equal to the product of (i) the excess, if any, of (A) the product of the exchange ratio multiplied by the Banner Closing Stock Price over (B) the applicable exercise price of such Pacific Financial stock option; and (ii) the number of shares of Pacific Financial common stock subject to such Pacific Financial stock option, less any required withholding taxes.

At the effective time, each Pacific Financial restricted stock unit (“RSU”) award that is outstanding as of immediately prior to the effective time will fully vest and any restrictions or risk of forfeiture will lapse. The shares of Pacific Financial common stock issuable upon the vesting and settlement of the Pacific Financial RSUs will be deemed to be issued and outstanding as of immediately prior to the effective time and will be treated in the merger in the same manner as other outstanding shares of Pacific Financial common stock at the effective time.

As of June 11, 2026, Pacific Financial had outstanding 10,025,137 shares of Pacific Financial common stock, 163,700 stock options and 58,255 RSUs. Based on the number of outstanding shares of Pacific Financial common stock and RSU awards as of June 11, 2026, Banner expects to issue approximately 2,654,957 shares of its common stock in the merger, excluding the additional shares of Banner common stock that may be issued in the merger to holders of Pacific Financial stock options that properly exercise their stock options in accordance with the merger agreement.

If the merger is consummated, based on the number of issued and outstanding shares of Banner common stock and shares of Pacific Financial common stock and RSU awards on June 11, 2026, we expect that Banner shareholders will own approximately 93%, and current Pacific Financial shareholders will own approximately 7%, of the outstanding shares of common stock of the combined company.

As part of the ongoing consideration and evaluation of its long-term prospects and strategies, Pacific Financial’s board of directors (which we refer to in this section as the “Pacific Financial Board”) and Pacific Financial’s senior management team have regularly reviewed and assessed Pacific Financial’s business strategies and objectives, including consideration of opportunities for strategic growth, whether through internal initiatives or through strategic transactions, as part of their continuous effort to grow Pacific Financial, enhance value for Pacific Financial shareholders, and deliver high quality products and services to Pacific Financial’s customers and communities. These periodic reviews have considered, among other things, developments and prospects affecting the financial services industry, in the regulatory environment, in the markets in which Pacific Financial operates and the economy overall, and in financial markets, and the implications of such developments for financial institutions generally and for Pacific Financial in particular. These reviews have also included assessments of the financial services industry, including the effects of changes in the competitive landscape and ongoing consolidation and the benefits and risks to Pacific Financial and its shareholders of strategic combinations with other banks compared to the benefits and risks of remaining independent.

In late September 2025, the Pacific Financial Board held its annual strategic planning meeting. Representatives of Piper Sandler were invited to present at the meeting regarding developments in the banking industry, an analysis of Pacific Financial’s stand-alone opportunities and value, an assessment of the merger and acquisition (referred to as, “M&A”) opportunities available to Pacific Financial, and an evaluation of the potential financial and strategic impacts of such combinations. Among other things, the meeting discussion included: (i) over the past 10 years Pacific Financial’s profitability has generally been in-line with the industry, while loan and deposit growth has generally been lower than other peer banks, (ii) looking forward, Pacific Financial has a stand-alone financial plan that is expected to grow the business and create value for Pacific Financial shareholders but its relatively small market capitalization and limited stock trading liquidity may continue to constrain Pacific Financial’s stock valuation and strategic opportunities, and (iii) an assessment that the pool of potential M&A partners (whether as targets for M&A, or as candidates to acquire Pacific Financial by merger) is small, has been declining, and is likely to continue to decline.

At the request of the Pacific Financial Board, in October 2025 Piper Sandler provided Pacific Financial with an overview of the M&A process as part of deliberations by the Pacific Financial Board and management team.

In December 2025, the Pacific Financial Board invited representatives of Piper Sandler to present at the Pacific Financial Board’s December board meeting and provide a more detailed financial and strategic analysis of Pacific Financial’s alternatives with regards to a potential acquisition of the company by merger as compared to continued independence, with a particular focus on the anticipated impacts to Pacific Financial shareholder value. Among other things, the meeting discussion included: (i) a review of Pacific Financial’s stand-alone projections and the estimated shareholder value outcomes that could reasonably be expected, (ii) an assessment of the most likely acquirors of Pacific Financial and the potential transaction values and deal terms that might be realized in a merger process, and (iii) a discussion of the process and timing of pursuing the potential acquisition of Pacific Financial by merger, along with the potential associated risks and steps that could be taken to mitigate the risks associated with the process. Following Piper Sandler’s presentation, Piper Sandler representatives left the meeting and the Pacific Financial Board discussed the potential benefits and risks associated with pursuing a merger transaction, including anticipated impacts on shareholders, customers, and employees. The Pacific Financial Board further engaged in discussion regarding valuation expectations, potential acquirors, potential transaction structure, and the pros and cons of engaging Piper Sandler to solicit proposals for a merger transaction from potentially interested parties. After extensive discussion, the Pacific Financial Board voted to proceed with a targeted process to solicit proposals for an acquisition by merger.

Following the meeting, Pacific Financial contacted Piper Sandler and expressed its interest in engaging Piper Sandler to assist Pacific Financial in pursuing a targeted solicitation of interest in acquiring the company by merger by marketing the opportunity to a selected group of potential buyers.

From late December 2025 to late January 2026, representatives of Piper Sandler conducted preliminary due diligence on Pacific Financial and with the help of Pacific Financial executive management, prepared to market Pacific Financial to a selected group of potential acquirors, as directed by the Pacific Financial Board.

On January 29, 2026, at the direction of Pacific Financial, representatives of Piper Sandler began contacting five potential merger partners. Of the five parties contacted, one indicated it had no interest in pursuing an opportunity

in the geographic region in which Pacific Financial operates and four, including Banner, executed a nondisclosure agreement, undertook preliminary due diligence, and held an exploratory meeting with Pacific Financial management. The form of nondisclosure agreement did not contain a standstill or similar provision.

By March 5, 2026, Pacific Financial received three non-binding indications of interest, each of which outlined the terms on which the potential acquiror would be willing to proceed with the acquisition of Pacific Financial. Also, around this time, one of the parties who executed the nondisclosure agreement informed Pacific Financial that they would not be making an acquisition proposal.

On March 10, 2026, the Pacific Financial Board held a special meeting in person to review the three non-binding indications of interest. At the meeting, representatives of Miller Nash, Pacific Financial’s outside legal counsel, provided the Pacific Financial Board an overview of their fiduciary duties and related matters. Also at the meeting, representatives of Piper Sandler walked the Pacific Financial Board through a thorough analysis of the three proposals. The Banner proposal included a 0.2566x exchange ratio which as of the meeting date was valued at $15.42 per Pacific Financial share, or $156 million in aggregate. The Party A proposal was valued at $16.42 per Pacific Financial share, or $166 million in aggregate as of the meeting date. The Party B proposal was valued at $14.07 per Pacific Financial share, or $142 million in aggregate as of the meeting date. All three of the proposals contemplated 100% stock consideration with a fixed exchange ratio and the Pacific Financial Board discussed how the value of the merger consideration would rise and fall based on changes in the market value of the potential acquiror’s stock. The Pacific Financial Board looked at the recent historical value of the three proposals and considered the potential future values of the three proposals based on the fundamentals of the institutions involved. Further, the Pacific Financial Board discussed the relative execution risks of the proposals and respective perceived differences and similarities of the business models, market familiarity, and operational risks of Banner, Party A, and Party B between each other and with those of Pacific Financial. Lengthy discussion ensued with questions and answers amongst the Pacific Financial Board, its management team and its financial and legal advisors, which discussion continued in executive session. At the conclusion of the meeting, the Pacific Financial Board was unanimous in its desire to pursue the Banner proposal, due to several factors, including: (i) a belief that the execution risk of the transaction with Banner was lower, (ii) the Banner business model was very similar to Pacific Financial and its operations appeared to be a strong strategic and geographic fit with Pacific Financial, and (iii) that Banner shares were perceived to offer good value for Pacific Financial shareholders, together with a significant amount of stock trading liquidity. The Pacific Financial Board directed Piper Sandler to undertake to negotiate further with Banner and seek an increased exchange ratio of 0.2700x, along with the inclusion or improvement of a selection of non-financial terms.

Over the course of the subsequent days, representatives of Piper Sandler undertook negotiations with representatives of Banner that resulted in Banner improving its offer. On March 13, 2026, the Pacific Financial Board held a special meeting to consider an updated nonbinding proposal from Banner. Banner’s updated proposal included a fixed exchange ratio of 0.2633x shares, which at the time was valued at $15.53 per Pacific Financial share or $157 million in aggregate, and other non-financial enhancements to the proposal. Following discussion, the Pacific Financial Board was unanimous in authorizing Pacific Financial management to execute the updated proposal from Banner, and it was executed later that day, commencing a 45-day period for exclusive due diligence and preparation of definitive documentation.

Banner’s full-scope due diligence of Pacific Financial began in mid-March 2026 and continued until the signing of the definitive merger agreement on April 30, 2026. The due diligence review consisted of a thorough review of Pacific Financial’s business, operations, books and records, along with numerous meetings with the Pacific Financial management team.

On March 30, 2026, Banner transmitted to Pacific Financial a first draft of the definitive merger agreement, as well as the bank merger agreement between Banner Bank and Bank of the Pacific and the voting and support agreement (together, the “ancillary agreements”). Banner continued its due diligence investigation and Banner and Pacific Financial, and their respective legal and financial advisors, continued to negotiate the legal documents from that point until their approval by the Pacific Financial Board on April 30, 2026, and execution of definitive agreements later that day.

On April 13, 2026, Pacific Financial and Banner executed an addendum to the initial proposal extending the exclusivity period for an additional seven days.

On April 15, 2026, a meeting occurred among Pacific Financial and Banner and their respective financial and legal advisors for purposes of Pacific Financial’s due diligence of Banner.

On April 22, 2026, at a regularly scheduled meeting of the Pacific Financial Board, representatives of Pacific Financial senior management along with representatives of Miller Nash and Piper Sandler provided the Pacific Financial Board with an update on the status of negotiations and the proposed transactions generally.

On April 24, 2026, Denise Portmann, Chief Executive Officer and President of Pacific Financial and Bank of the Pacific, received a letter from Banner outlining the general terms of an offer to become an executive vice present of Banner Bank at the effective time of the bank merger. The parties agreed that the final terms of Ms. Portmann’s employment would be agreed upon during the period between the signing of the merger agreement and closing. Banner informed Pacific Financial that it did not expect to make a similar employment offer to any other Pacific Financial director or executive officer.

On April 28, 2026, the Banner Board of Directors held a meeting and unanimously approved the merger agreement with Pacific Financial and authorized Banner officers to finalize and execute the merger agreement and the ancillary agreements.

On April 30, 2026, the Pacific Financial Board held a special meeting to consider the negotiated terms of the proposed merger between Pacific Financial and Banner and entry into the merger agreement and other transaction documents in connection with the proposed merger. Members of Pacific Financial’s management and representatives of Miller Nash and Piper Sandler were also in attendance at the meeting. At this meeting, representatives of Miller Nash first provided a brief update overview of the fiduciary duties of directors. Next, representatives of Piper Sandler reviewed with the Pacific Financial Board the detailed financial analysis summarized below under “—Opinion of Pacific Financial’s financial advisor.” Representatives of Piper Sandler also rendered to the Pacific Financial Board its opinion, which was initially rendered verbally and subsequently confirmed in writing dated April 30, 2026, to the effect that, as of such date and based upon and subject to the assumptions made, procedures followed, matters considered, and qualifications and limitations on the review undertaken by Piper Sandler as set forth in its written opinion, the per share merger consideration in the proposed merger was fair, from a financial point of view, to the holders of Pacific Financial common stock. For more information, see the section entitled “—Opinion of Pacific Financial’s financial advisor” and the full text of the opinion provided in Appendix B to this proxy statement/prospectus. Representatives of Miller Nash discussed the Pacific Financial Board’s fiduciary duties and related matters and then reviewed with the Pacific Financial Board the final terms of the proposed merger agreement and other transaction documents. Among other matters considered, the Pacific Financial Board reviewed the specific terms of the merger agreement and the ancillary agreements, the consideration to be received by Pacific Financial’s shareholders, the price and historical performance of Banner’s common stock, current market conditions and Piper Sandler financial analysis. The Pacific Financial Board noted that, based on the closing price of Banner common stock on April 29, 2026, the aggregate transaction value of the proposed merger was approximately $177 million. Following further discussion, during which the directors considered the matters reviewed and discussed at that meeting and all prior meetings, including the factors described under “The Merger—Pacific Financial’s reasons for the merger and recommendation of the Pacific Financial Board,” the Pacific Financial Board unanimously (i) determined that the merger agreement and the transactions contemplated thereby, including the merger, are advisable and in the best interests of Pacific Financial and its shareholders, (ii) approved the merger agreement, the merger and the other transactions contemplated thereby, (iii) approved the ancillary agreements, (iv) authorized the execution and delivery of the merger agreement and the ancillary agreements, (v) directed that the merger agreement be submitted to the holders of Pacific Financial common stock for approval, and (vi) recommended approval of the merger agreement by the holders of Pacific Financial common stock.

Later in the day on April 30, 2026, the merger agreement and the ancillary agreements were executed and delivered by Banner and Pacific Financial. The transaction was publicly announced in a press release jointly issued by Banner and Pacific Financial on the afternoon of April 30, 2026.

At a meeting held on April 30, 2026, the Pacific Financial Board unanimously determined that the merger, on the terms and conditions set forth in the merger agreement, was in the best interests of Pacific Financial and its shareholders. In reaching this determination and making the related decision to approve and adopt the merger agreement and to recommend that Pacific Financial’s shareholders vote “FOR” the proposal to approve the merger agreement, the Pacific Financial Board evaluated the merger and the merger agreement in consultation with the management of Pacific Financial and Pacific Financial’s financial advisor and legal counsel, and considered a variety of factors, including the following factors that the Pacific Financial Board viewed as generally supporting its determination and decisions:

The foregoing discussion of the information and factors considered by the Pacific Financial Board to approve the merger agreement and recommend that Pacific Financial’s shareholders vote in favor of the proposal to approve the merger agreement includes the material factors considered by the Pacific Financial Board in connection with its evaluation of the merger, but is not intended to be exhaustive. In reaching its decision to approve and recommend the transaction, the Pacific Financial Board based its determination on the totality of the information available to it and did not quantify or assign any relative or specific weights to the factors considered in reaching that determination. In addition, individual directors may have given different weights to different factors.

After careful consideration, the Pacific Financial Board unanimously determined that the merger, on the terms and conditions set forth in the merger agreement, was in the best interests of Pacific Financial and its shareholders.

The Pacific Financial Board unanimously recommends that Pacific Financial shareholders vote “FOR” the proposal to approve the merger agreement and “FOR” the adjournment proposal.

This summary of the reasoning of the Pacific Financial Board and other information presented in this section are forward-looking in nature and, therefore, should be read in light of the factors discussed under the heading “Special Note Regarding Forward-Looking Statements.”

Pacific Financial retained Piper Sandler to act as financial advisor to the Pacific Financial Board in connection with Pacific Financial’s consideration of a possible business combination. Pacific Financial selected Piper Sandler to act as its financial advisor because Piper Sandler is a nationally recognized investment banking firm which specializes in financial institutions. In the ordinary course of its investment banking business, Piper Sandler is regularly engaged in the valuation of financial institutions and their securities in connection with mergers and acquisitions and other corporate transactions.

Piper Sandler acted as financial advisor to the Pacific Financial Board in connection with the proposed merger and participated in certain of the negotiations leading to the execution of the merger agreement. At the April 30, 2026 meeting at which the Pacific Financial Board considered the merger and the merger agreement, Piper Sandler delivered to the Pacific Financial Board its oral opinion, which was subsequently confirmed in writing, to the effect that, as of such date, the per share merger consideration was fair to the holders of Pacific Financial’s common stock from a financial point of view. The full text of Piper Sandler’s opinion is attached as Appendix B to this proxy statement/prospectus. The opinion outlines the procedures followed, assumptions made, matters considered and

qualifications and limitations on the review undertaken by Piper Sandler in rendering its opinion. The description of the opinion set forth below is qualified in its entirety by reference to the full text of the opinion. Holders of Pacific Financial common stock are urged to read the entire opinion carefully in connection with their consideration of the proposed merger.

Piper Sandler’s opinion was directed to the Pacific Financial Board in connection with its consideration of the merger and the merger agreement and does not constitute a recommendation to any shareholder of Pacific Financial as to how any such shareholder should vote at any meeting of shareholders called to consider and vote upon the approval of the merger and the merger agreement. Piper Sandler’s opinion was directed only to the fairness, from a financial point of view, of the per share merger consideration to the holders of Pacific Financial common stock and did not address the underlying business decision of Pacific Financial to engage in the merger, the form or structure of the merger or any other transactions contemplated in the merger agreement, the relative merits of the merger as compared to any other alternative transactions or business strategies that might exist for Pacific Financial or the effect of any other transaction in which Pacific Financial might engage. Piper Sandler also did not express any opinion as to the fairness of the amount or nature of the compensation to be received in the merger by any officer, director or employee of Pacific Financial or Banner, or any class of such persons, if any, relative to the compensation to be received in the merger by any other shareholder. Piper Sandler’s opinion was approved by Piper Sandler’s fairness opinion committee.

In connection with its opinion, Piper Sandler reviewed and considered, among other things:

Piper Sandler also discussed with certain members of the senior management of Pacific Financial and its representatives the business, financial condition, results of operations and prospects of Pacific Financial and held similar discussions with certain members of the senior management of Banner and its representatives regarding the business, financial condition, results of operations and prospects of Banner.

In performing its review, Piper Sandler relied upon the accuracy and completeness of all of the financial and other information that was available to and reviewed by Piper Sandler from public sources, that was provided to Piper Sandler by Pacific Financial, Banner or their respective representatives, or that was otherwise reviewed by Piper Sandler, and Piper Sandler assumed such accuracy and completeness for purposes of rendering its opinion without any independent verification or investigation. Piper Sandler relied on the assurances of the respective managements of Pacific Financial and Banner that they were not aware of any facts or circumstances that would have made any of such information inaccurate or misleading. Piper Sandler was not asked to and did not undertake an independent verification of any of such information and Piper Sandler did not assume any responsibility or liability for the accuracy or completeness thereof. Piper Sandler did not make an independent evaluation or perform an appraisal of the specific assets, the collateral securing assets or the liabilities (contingent or otherwise) of Pacific Financial or Banner, nor was Piper Sandler furnished with any such evaluations or appraisals. Piper Sandler rendered no opinion or evaluation on the collectability of any assets or the future performance of any loans of Pacific Financial or Banner, nor any of their respective subsidiaries. Piper Sandler did not make an independent evaluation of the adequacy of the allowance for credit losses of Pacific Financial or Banner, any of their respective subsidiaries or of the combined entity after the merger, and Piper Sandler did not review any individual credit files relating to Pacific Financial or Banner or any of their respective subsidiaries. Piper Sandler assumed, with Pacific Financial’s consent, that the respective allowances for credit losses for both Pacific Financial and Banner and their respective subsidiaries were adequate to cover such losses and would be adequate on a pro forma basis for the combined entity.

In preparing its analyses, Piper Sandler used certain internal financial projections for Pacific Financial for the years ending December 31, 2026 through December 31, 2030, including estimated share repurchases for Pacific Financial common stock for the year ending December 31, 2026 and estimated dividends per share for Pacific Financial common stock for the years ending December 31, 2026 through December 31, 2030, as confirmed by the senior management of Pacific Financial. In addition, Piper Sandler used publicly available median analyst earnings per share estimates for Banner for the nine month period ending December 31, 2026 and the year ending December 31, 2027 with an estimated long-term annual asset and net income growth rate for Banner for the years thereafter, as well as estimated dividends per share for Banner common stock for the years ending December 31, 2026 through December 31, 2030, as provided by the senior management of Banner and confirmed for use in Piper Sandler’s analysis by the senior management of Pacific Financial. Piper Sandler also received and used in its pro forma analyses certain assumptions relating to transaction expenses, cost savings and purchase accounting adjustments, as well as adjustments for current expected credit losses (CECL) accounting standards, as confirmed by the senior management of Banner. With respect to the foregoing information, the senior management of Pacific Financial confirmed to Piper Sandler that such information reflected (or in the case of the publicly available analyst estimates referred to above, was consistent with) the best currently available estimates and judgements of senior management as to the future financial performance of Pacific Financial and Banner, respectively, and Piper Sandler assumed that the financial results reflected in such information would be achieved. Piper Sandler expressed no opinion as to such information, or the assumptions on which such information was based. Piper Sandler also assumed that there had been no material change in Pacific Financial’s or Banner’s assets, financial condition, results of operations, business or prospects since the date of the most recent financial statements made available to Piper Sandler. Piper Sandler assumed in all respects material to its analyses that Pacific Financial and Banner would remain as going concerns for all periods relevant to its analyses.

Piper Sandler also assumed, with Pacific Financial’s consent, that (i) each of the parties to the merger agreement would comply in all material respects with all material terms and conditions of the merger agreement and all related agreements, that all of the representations and warranties contained in such agreements were true and correct in all material respects, that each of the parties to such agreements would perform in all material respects all of the covenants and other obligations required to be performed by such party under such agreements and that the conditions precedent in such agreements were not and would not be waived, (ii) in the course of obtaining the necessary regulatory or third party approvals, consents and releases with respect to the merger, no delay, limitation, restriction or condition would be imposed that would have an adverse effect on Pacific Financial, Banner, the merger or any related transactions, and (iii) the merger and any related transactions would be consummated in accordance with the terms of the merger agreement without any waiver, modification or amendment of any material term, condition or agreement thereof and in compliance with all applicable laws and other requirements. Finally, with Pacific Financial’s consent, Piper Sandler

relied upon the advice that Pacific Financial received from its legal, accounting and tax advisors as to all legal, accounting and tax matters relating to the merger and the other transactions contemplated by the merger agreement. Piper Sandler expressed no opinion as to any such matters.

Piper Sandler’s opinion was necessarily based on financial, economic, regulatory, market and other conditions as in effect on, and the information made available to Piper Sandler as of, the date thereof. Events occurring after the date thereof could materially affect Piper Sandler’s opinion. Piper Sandler has not undertaken to update, revise, reaffirm or withdraw its opinion or otherwise comment upon events occurring after the date thereof. Piper Sandler expressed no opinion as to the trading value of Pacific Financial common stock or Banner common stock at any time or what the value of Banner common stock would be once it is actually received by the holders of Pacific Financial common stock.

In rendering its opinion, Piper Sandler performed a variety of financial analyses. The summary below is not a complete description of all the analyses underlying Piper Sandler’s opinion or the presentation made by Piper Sandler to the Pacific Financial Board, but is a summary of the material analyses performed and presented by Piper Sandler. The summary includes information presented in tabular format. In order to fully understand the financial analyses, these tables must be read together with the accompanying text. The tables alone do not constitute a complete description of the financial analyses. The preparation of a fairness opinion is a complex process involving subjective judgments as to the most appropriate and relevant methods of financial analysis and the application of those methods to the particular circumstances. The process, therefore, is not necessarily susceptible to a partial analysis or summary description. Piper Sandler believes that its analyses must be considered as a whole and that selecting portions of the factors and analyses without considering all the factors and analyses, or attempting to ascribe relative weights to some or all such factors and analyses, could create an incomplete view of the evaluation process underlying its opinion. Also, no company included in Piper Sandler’s comparative analyses described below is identical to Pacific Financial or Banner and no transaction is identical to the merger. Accordingly, an analysis of comparable companies or transactions involves complex considerations and judgments concerning differences in financial and operating characteristics of the companies and other factors that could affect the public trading values or transaction values, as the case may be, of Pacific Financial and Banner and the companies to which they were compared. In arriving at its opinion, Piper Sandler did not attribute any particular weight to any analysis or factor that it considered. Rather, Piper Sandler made qualitative judgments as to the significance and relevance of each analysis and factor. Piper Sandler did not form an opinion as to whether any individual analysis or factor (positive or negative) considered in isolation supported or failed to support its opinion, rather, Piper Sandler made its determination as to the fairness of the per share merger consideration to the holders of Pacific Financial common stock on the basis of its experience and professional judgment after considering the results of all its analyses taken as a whole.

In performing its analyses, Piper Sandler also made numerous assumptions with respect to industry performance, business and economic conditions and various other matters, many of which cannot be predicted and are beyond the control of Pacific Financial, Banner, and Piper Sandler. The analyses performed by Piper Sandler are not necessarily indicative of actual values or future results, both of which may be significantly more or less favorable than suggested by such analyses. Piper Sandler prepared its analyses solely for purposes of rendering its opinion and provided such analyses to the Pacific Financial Board at its April 30, 2026 meeting. Estimates on the values of companies do not purport to be appraisals or necessarily reflect the prices at which companies or their securities may actually be sold. Such estimates are inherently subject to uncertainty and actual values may be materially different. Accordingly, Piper Sandler’s analyses do not necessarily reflect the value of Pacific Financial or Banner common stock or the prices at which Pacific Financial or Banner common stock may be sold at any time. The analyses of Piper Sandler and its opinion were among a number of factors taken into consideration by the Pacific Financial Board in making its determination to approve the merger agreement and the analyses described below should not be viewed as determinative of the decision of the Pacific Financial Board with respect to the fairness of the per share merger consideration.

Piper Sandler reviewed the financial terms of the proposed merger. Pursuant to the terms of the merger agreement, at the effective time of the merger each share of Pacific Financial common stock issued and outstanding immediately prior to the effective time of the transaction, except for certain shares as set forth in the merger agreement, shall be converted into the right to receive 0.2633 of a share of Banner common stock. Piper Sandler calculated an implied purchase price per Pacific Financial share of $17.44 and an aggregate implied transaction value of approximately $177.0 million, consisting of the implied value of 10,082,695 shares of Pacific Financial common stock and equivalents¹, as well as the implied value of 170,200 in the money Pacific Financial stock options² and based on the closing price of Banner common stock on April 29, 2026 of $66.25 per share. Based upon financial information for Pacific Financial as of or for the last twelve months (“LTM”) ended March 31, 2026 and the closing price of Pacific Financial’s common stock on April 29, 2026, Piper Sandler calculated the following implied transaction metrics:

Piper Sandler reviewed the publicly available historical reported trading prices of Pacific Financial common stock and Banner common stock for the one-year and three-year periods ended April 29, 2026. Piper Sandler then compared the relationship between the movements in the price of Pacific Financial common stock and Banner common stock, respectively, to movements in their respective peer groups (as described below) as well as certain stock indices.

Piper Sandler used publicly available information to compare selected financial information for Pacific Financial with a group of banks selected by Piper Sandler. The Pacific Financial peer group included nationwide banks with common stock traded on the NASDAQ or NYSE exchanges with total assets between $1.0 billion and $3.0 billion, interest expense / average assets less than 1.70%, noninterest income / average assets less than 1.00%, and noninterest expense / average assets greater than 2.25%, with all criteria applied to the twelve months ended December 31, 2025, but excluded announced merger targets, mutual holding companies, First Northern Community Bancorp (due to uplisting to the NASDAQ exchange after the 2025 calendar year), and Avidia Bancorp, Inc., FB Bancorp, Inc., and SR Bancorp, Inc. due to mutual conversions within the last 5 years (since January 1, 2021) (the “Pacific Financial Peer Group”). The Pacific Financial Peer Group consisted of the following companies:

The analysis compared publicly available financial for Pacific Financial with corresponding data for the Pacific Financial Peer Group as of or for the twelve months ended March 31, 2026 (unless otherwise noted) with pricing data as of April 29, 2026. The table below sets forth the data for Pacific Financial and the median, mean, low and high data for the Pacific Financial Peer Group. Certain financial data prepared by Piper Sandler, as referenced in the table presented below, may not correspond to the data presented in Pacific Financial’s historical financial statements, as a result of the different periods, assumptions and methods used by Piper Sandler to compute the financial data presented.

Piper Sandler used publicly available information to perform a similar analysis for Banner by comparing selected financial information for Banner with a group of banks selected by Piper Sandler. The Banner peer group included nationwide banks with common stock traded on the NASDAQ or NYSE exchanges with total assets between $10.0 billion and $20.0 billion as of March 31, 2026 (unless otherwise noted), but excluded announced merger targets, mutual holding companies, LendingClub Corporation (due to its non-traditional business model), and CVB Financial Corp. and OceanFirst Financial Corp. due to their recently announced or completed M&A transactions expected to bring pro forma assets over $20.0 billion (the “Banner Peer Group”). The Banner Peer Group consisted of the following companies:

The analysis compared publicly available financial information for Banner with corresponding data for the Banner Peer Group as of or for the twelve months ended March 31, 2026 (unless otherwise noted) with pricing data as of April 29, 2026. The table below sets forth the data for Banner and the median, mean, low and high data for the Banner Peer Group. Certain financial data prepared by Piper Sandler, as referenced in the table presented below, may not correspond to the data presented in Banner’s historical financial statements, as a result of the different periods, assumptions and methods used by Piper Sandler to compute the financial data presented.

Piper Sandler reviewed a group of bank merger and acquisition transactions. The group consisted of nationwide bank transactions announced between April 29, 2025 and April 29, 2026 with target total assets between $1.0 billion and $3.0 billion at the time of announcement, but excluded thrift merger conversions, government-assisted transactions, deals without reported deal value, deals with undisclosed buyers, and transactions in which the target had negative LTM core return on average assets (as calculated by S&P Capital IQ Pro) as of the most recent financials available at the time of announcement (the “Nationwide Precedent Transactions”).

The Nationwide Precedent Transactions group was composed of the following transactions:

Using the latest publicly available information prior to the announcement of the relevant transaction, Piper Sandler reviewed the following transaction metrics: transaction price to LTM earnings, transaction price to tangible book value, core deposit premium, and 1-day market premium. Piper Sandler compared the indicated transaction metrics for the transaction to the median, mean, low and high metrics of the Nationwide Precedent Transactions group.

Piper Sandler performed an analysis that estimated the net present value of a share of Pacific Financial common stock assuming Pacific Financial performed in accordance with certain internal financial projections for Pacific Financial for the years ending December 31, 2026 through December 31, 2030, including estimated share repurchases for Pacific Financial common stock for the year ending December 31, 2026 and estimated dividends per share for Pacific Financial common stock for the years ending December 31, 2026 through December 31, 2030, as confirmed by the senior management of Pacific Financial. To approximate the terminal value of a share of Pacific Financial common stock on December 31, 2030, Piper Sandler applied price to earnings multiples ranging from 9.0x to 13.0x and multiples of tangible book value ranging from 100% to 160%. The terminal values were then discounted to present values using different discount rates ranging from 9.0% to 13.0%, which were chosen to reflect different assumptions regarding required rates of return of holders or prospective buyers of Pacific Financial common stock. As illustrated in the following tables, the analysis indicated an imputed range of values per share of Pacific Financial common stock of $11.65 to $18.46 when applying multiples of earnings and $11.24 to $19.39 when applying multiples of tangible book value.

Piper Sandler also considered how this analysis would be affected by changes in the underlying assumptions, including variations with respect to projected earnings. To illustrate this impact, Piper Sandler performed a similar analysis, assuming Pacific Financial’s earnings varied from 20.0% above projections to 20.0% below projections. This analysis resulted in the following range of per share values for Pacific Financial’s common stock, applying the price to earnings multiples range of 9.0x to 13.0x referred to above and a discount rate of 11.03%.

Piper Sandler also performed an analysis that estimated the net present value per share of Banner common stock, assuming Banner performed in accordance with publicly available median analyst earnings per share estimates for Banner for the nine month period ending December 31, 2026 and the year ending December 31, 2027, with an estimated long-term annual asset and net income growth rate for Banner for the years thereafter, as well as estimated dividends per share for Banner common stock for the years ending December 31, 2026 through December 31, 2030, as provided by the senior management of Banner and confirmed for use in Piper Sandler’s analysis by the senior management of Pacific Financial. To approximate the terminal value of a share of Banner common stock on December 31, 2030, Piper Sandler applied price to earnings multiples ranging from 10.0x to 15.0x and multiples of tangible book value ranging from 120% to 200%. The terminal values were then discounted to present values using different discount rates ranging from 8.5% to 12.5%, which were chosen to reflect different assumptions regarding required rates of return of holders or prospective buyers of Banner common stock. As illustrated in the following tables, the analysis indicated an imputed range of values per share of Banner common stock of $51.60 to $86.76 when applying multiples of earnings and $55.45 to $103.01 when applying multiples of tangible book value.