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Business Context and Reporting Period

Company: Prosperity Bancshares, Inc. (Prosperity)
Filing Type: Form 8-K (Current Report)
Date of Report: January 28, 2026
Event: Announcement of a definitive merger agreement with Stellar Bancorp, Inc. (Stellar). Under the terms of the Agreement and Plan of Merger dated January 27, 2026, Stellar will merge with and into Prosperity, with Prosperity continuing as the surviving corporation. Subsequently, Stellar Bank will merge with and into Prosperity Bank.

Key Financial Metrics

This filing is a current report regarding a corporate transaction and does not contain audited financial statements, revenue, profit, cash flow, margin, debt, or liquidity metrics for the reporting period. The document references that supplemental information regarding the transaction will be provided in investor presentations (Exhibit 99.2) and future filings (Form S-4), but specific financial values are not included in this text.

Material Changes

Corporate Structure: The primary material change is the execution of the Merger Agreement, which will result in the consolidation of Stellar Bancorp, Inc. and its subsidiary, Stellar Bank, into Prosperity Bancshares, Inc. and Prosperity Bank, respectively.
Securities Issuance: The transaction contemplates the issuance of Prosperity common stock to Stellar shareholders, which may result in dilution.

Guidance, Outlook, Risks, and Contingencies

Outlook and Process: Prosperity intends to file a Registration Statement on Form S-4 with the SEC, which will include a Proxy Statement/Prospectus for Stellar shareholders. The transaction is subject to various closing conditions, including shareholder approval by Stellar and required governmental approvals.
Risks and Contingencies: The filing outlines significant risks that could cause actual results to differ from expectations, including:

• Failure to realize anticipated cost savings and synergies or delays in integration.
• Disruption to business operations during the pendency of the transaction.
• Failure to obtain necessary shareholder or governmental approvals.
• Dilution of existing Prosperity shareholders due to new stock issuance.
• Increased transaction costs or unexpected legal/regulatory proceedings.
• Diversion of management attention from ongoing operations.

Forward-Looking Statements: The document contains forward-looking statements regarding future financial performance, integration benefits, and transaction timing, which are subject to inherent uncertainties and are not guarantees.

Investor Verification Checklist

• Verify the specific exchange ratio and valuation terms in the upcoming Form S-4 Registration Statement and Proxy Statement/Prospectus.
• Confirm the status of required regulatory approvals and shareholder votes for Stellar Bancorp, Inc.
• Review the detailed integration plan and synergy targets in the investor presentation (Exhibit 99.2) referenced in the filing.
• Monitor for any material changes to the Merger Agreement or termination events as disclosed in future 8-K filings.
• Assess the potential dilution impact on Prosperity's earnings per share once the transaction closes.