Stellar Bancorp, Inc.

false 0001473844 0001473844 2026-05-20 2026-05-20 UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Form 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event Reported): May 20, 2026 Stellar Bancorp, Inc. (Exact Name of Registrant as Specified in Charter) Texas 001-38280 20-8339782 (State or Other Jurisdiction of Incorporation) (Commission File Number) (I.R.S. Employer Identification Number) 9 Greenway Plaza , Suite 110 Houston , Texas 77046 (Address of Principal Executive Offices) (Zip Code) (713) 210-7600 (Registrant’s telephone number, including area code) (Former name or former address, if changed since last report) Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions: ☒ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) ☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12) ☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)) ☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c)) Securities registered pursuant to Section 12(b) of the Act: Title of each class Trading Symbol(s) Name of each exchange on which registered Common stock, par value $0.01 per share STEL New York Stock Exchange (indicate by check) NYSE Texas Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter). Emerging growth company ☐ If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐ Item 8.01 Other Events. As announced on January 28, 2026, Stellar Bancorp, Inc., a Texas corporation (“Stellar” or the “Company”), entered into an Agreement and Plan of Merger, dated January 27, 2026 (the “Merger Agreement”), with Prosperity Bancshares, Inc., a Texas corporation (“Prosperity”), pursuant to which Stellar will merge with and into Prosperity (the “Merger”), with Prosperity as the surviving corporation in the Merger. Immediately following the Merger, Stellar’s wholly owned banking subsidiary, Stellar Bank, will merge with and into Prosperity’s wholly owned banking subsidiary, Prosperity Bank (the “Bank Merger”), which will continue as the surviving bank in the Bank Merger (collectively, the “Proposed Transaction”). In connection with the Proposed Transaction, Prosperity filed with the Securities and Exchange Commission (the “SEC”) on April 3, 2026, a registration statement on Form S-4, File No. 333-294882, as amended on April 17, 2026, and which was declared effective by the SEC on April 21, 2026, containing a preliminary prospectus of Prosperity that also constitutes a preliminary proxy statement of Stellar, and Stellar filed a definitive proxy statement and Prosperity filed a final prospectus with the SEC, dated April 21, 2026 (the “proxy statement/prospectus”), with respect to the special meeting of Stellar shareholders scheduled to be held on May 27, 2026. Stellar first mailed the proxy statement/prospectus to its shareholders on or about April 23, 2026. Litigation Related to the Proposed Transaction Following the announcement of the Proposed Transaction, as of the date of this Current Report on Form 8-K, three lawsuits challenging the Proposed Transaction have been filed (each, a “Lawsuit” and, collectively, the “Lawsuits”). The first Lawsuit, captioned Jackson v. Stellar Bancorp, Inc., et al. , No. 652644/2026, was filed in the Supreme Court of the State of New York on May 5, 2026. The second Lawsuit, captioned Kent v. Stellar Bancorp, Inc., et al. , No. 652658/2026, was filed in the Supreme Court of the State of New York on May 5, 2026. The third Lawsuit, captioned Zalvin v. Stellar Bancorp, Inc., et al., No. 652804/2026, was filed in the Supreme Court of the State of New York on May 13, 2026. In addition, Stellar has received demand letters from counsel representing purported shareholders of Stellar (the “Demand Letters” and, together with the Lawsuits, the “Matters”). The Matters each allege that, among other things, the proxy statement/prospectus contains certain disclosure deficiencies and/or incomplete information regarding the Proposed Transaction. Stellar and Prosperity believe that the claims asserted in the Matters are without merit and that no additional disclosure in the proxy statement/prospectus is required or necessary under applicable laws. However, in order to avoid the risk that the Matters delay or otherwise adversely affect the Proposed Transaction, and to minimize the costs, risks and uncertainties inherent in litigation, and without admitting any liability or wrongdoing, Stellar and Prosperity hereby make additional disclosures (the “Supplemental Disclosures”) to supplement the disclosures contained in the proxy statement/prospectus. Stellar, Prosperity and their respective boards of directors deny all allegations in the Matters that any additional disclosure was or is required or that they have violated any laws or breached any duties to their shareholders in connection with the proxy statement/prospectus, and none of the Supplemental Disclosures nor any other disclosure in this Current Report on Form 8-K should be construed as an admission of the legal necessity or materiality under applicable laws of any Supplemental Disclosures. SUPPLEMENT TO PROXY STATEMENT/PROSPECTUS The information set forth below supplements the proxy statement/prospectus and should be read in conjunction with the proxy statement/prospectus, which should be read in its entirety. To the extent that information herein differs from or updates information contained in the proxy statement/prospectus, the information contained herein supersedes the information contained in the proxy statement/prospectus. Except as otherwise described in the below supplemental disclosures or the documents referred to, contained in or incorporated by reference herein, the proxy statement/prospectus, the annexes to the proxy statement/prospectus and the documents referred to, contained in or incorporated by reference in the proxy statement/prospectus are not otherwise modified, supplemented or amended. All page references below are to pages in the proxy statement/prospectus, and terms used below shall have the meanings set forth in the proxy statement/prospectus (unless otherwise defined below). For clarity, new text within restated paragraphs and tables from the proxy statement/prospectus is underlined, while deleted text is stricken-through. 1. The disclosure under the section entitled “The Merger—Background of the Merger” in the proxy statement/prospectus is hereby amended by adding the following underlined language and deleting the stricken language in the last paragraph on page 55 of the proxy statement/prospectus: From time to time, Mr. Franklin has met with executive officers of other financial institutions to have general discussions about the banking industry, including at industry and investor conferences. Prior to the discussions with KBW, Mr. Franklin had scheduled a lunch meeting with the Chief Operating Executive Officer of a publicly traded regional bank holding company (“Company B”) to take place on September 23, 2025. Company B was contacted by KBW in advance of the lunch meeting and expressed interest in a potential business combination. On September 23, 2025, Mr. Franklin met with the Chief Executive Officer of Company B for lunch. On September 26, 2025, Stellar and Company B executed a non-disclosure agreement to permit further discussio