above. 99.1 Press Release, dated July 28, 2026, issued by Community Financial System, Inc. 104 Cover Page Interactive Data File (embedded in the cover page formatted in Inline XBRL) SIGNATURES Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. Community Financial System, Inc. By: /s/ Marya Burgio Wlos Name: Marya Burgio Wlos Title: Executive Vice President and C…

Other Events. On June 1, 2026, Community Financial System, Inc. (the “Company”) announced that its wholly-owned subsidiary, Community Bank, N.A. (“Community Bank”), completed its acquisition of ClearPoint Federal Bank & Trust, a federally chartered savings association (“ClearPoint”), as contemplated by the previously announced Agreement and Plan of Merger, as amended, dated as of January 14, 2026, by and among Community Bank, ClearPoint, and Michael Devlin, solely in his capacity as the repre…

above. 99.1 Press Release, dated April 29, 2026, issued by Community Financial System, Inc. 104 Cover Page Interactive Data File (embedded in the cover page formatted in Inline XBRL) SIGNATURES Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. Community Financial System, Inc. By: /s/ Marya Burgio Wlos Name: Marya Burgio Wlos Title: Executive Vice President and…

Director — Brenda M. Hall: Ms. Brenda M. Hall was elected as a new independent director.

above. 99.1 Press Release, dated January 27, 2026, issued by Community Financial System, Inc. 104 Cover Page Interactive Data File (embedded in the cover page formatted in Inline XBRL) SIGNATURES Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. Community Financial System, Inc. By: /s/ Marya Burgio Wlos Name: Marya Burgio Wlos Title: Executive Vice President an…

Chief Banking Officer — Jeffrey M. Levy: The filing describes a planned retirement of a senior officer (SVP/CBO) with a named internal successor and a transition consulting agreement, indicating an orderly succession rather than a sudden loss.

Other Events On December 17, 2025, the Company’s Board of Directors approved its annual stock repurchase program authorizing the repurchase, at the discretion of senior management and subject to approval by the Company’s regulators, of up to 2,633,000 shares of the Company’s common stock during the twelve-month period starting January 1, 2026. Such repurchases may be made at the discretion of senior management depending on market conditions and other relevant factors and will be acquired thro…

Other Matters. On November 7, 2025, Community Bank, N.A. (“Community Bank”), the wholly-owned banking subsidiary of Community Financial System, Inc. (the “Company”), completed its acquisition of seven branches in the Allentown, Pennsylvania area from Santander Bank, N.A. (“Santander Bank”), as contemplated by the previously announced Purchase and Assumption Agreement, by and between Community Bank and Santander Bank, dated as of June 24, 2025. In addition, Nottingham Investment Services, Inc.…

above. 99.1 Press Release, dated October 21, 2025, issued by Community Financial System, Inc. 104 Cover Page Interactive Data File (embedded in the cover page formatted in Inline XBRL) SIGNATURES Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. Community Financial System, Inc. By: /s/ Marya Burgio Wlos Name: Marya Burgio Wlos Title: Executive Vice President an…

Director — John A. Vaccaro: The filing discloses the election of a new independent director to the Board, which is a routine governance event and not a departure of a senior executive.

Other Matters. On September 8, 2025, Community Financial System, Inc. (the “Company”) issued a press release announcing that it has made a minority investment in Leap Holdings, Inc., a Delaware corporation (“Leap”). The Company acquired approximately $37,350,000 in various classes of preferred and common stock. A copy of the press release, dated September 8, 2025, issued by the Company, is attached hereto as Exhibit 99.1.

Chief Banking Officer — Jeffrey M. Levy: The Chief Banking Officer is retiring with a named internal successor (Matthew Durkee) already identified, indicating an orderly succession rather than a sudden loss of leadership.

above. 99.1 Press Release, dated July 22, 2025, issued by Community Financial System, Inc. 104 Cover Page Interactive Data File (embedded in the cover page formatted in Inline XBRL) SIGNATURES Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. Community Financial System, Inc. By: /s/ Marya Burgio Wlos Name: Marya Burgio Wlos Title: Executive Vice President and C…

Other Matters. On June 24, 2025, Community Bank, N.A. (the “Community Bank”), the wholly-owned banking subsidiary of Community Financial System, Inc. (the “Company”), entered into a Purchase and Assumption Agreement (the “Agreement”) with Santander Bank, N.A. (“Santander”) pursuant to which Community Bank agreed to acquire certain assets and assume certain liabilities of seven Santander branch offices located in Allentown, Pennsylvania area (the “Branches”). Subject to the terms of the Agreem…

above. 99.1 Press Release, dated April 29, 2025, issued by Community Financial System, Inc. 104 Cover Page Interactive Data File (embedded in the cover page formatted in Inline XBRL) SIGNATURES Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. Community Financial System, Inc. By: /s/ Marya Burgio Wlos Name: Marya Burgio Wlos Title: Executive Vice President and…

CFO — Joseph E. Sutaris: The filing announces the retirement of the CFO, Joseph E. Sutaris, and the appointment of a named successor, Marya Burgio Wlos, with a defined transition period, indicating an orderly succession rather than a sudden loss of leadership.

Director — Susan E. Skerritt: A board member is retiring from the board at the next annual meeting, which is a routine governance change rather than a loss of a senior executive officer.

above. 99.1 Press Release, dated January 21, 2025, issued by Community Financial System, Inc. 104 Cover Page Interactive Data File (embedded in the cover page formatted in Inline XBRL) SIGNATURES Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. Community Financial System, Inc. By: /s/ Joseph E. Sutaris Name: Joseph E. Sutaris Title: Executive Vice President an…

Other Events On December 18, 2024, the Board of Directors of Community Financial System, Inc. (the “Company”) approved its annual stock repurchase program authorizing the repurchase, at the discretion of senior management and subject to approval by the Company’s regulators, of up to 2,628,000 shares of the Company’s common stock during the twelve-month period starting January 1, 2025. Such repurchases may be made at the discretion of senior management depending on market conditions and other…

CFO — Joseph E. Sutaris: The CFO is retiring for personal reasons with a planned transition period and no disagreement with the company, indicating an orderly succession rather than a sudden loss.

above. 99.1 Press Release, dated October 22, 2024, issued by Community Financial System, Inc. 104 Cover Page Interactive Data File (embedded in the cover page formatted in Inline XBRL) SIGNATURES Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. Community Financial System, Inc. By: /s/ Joseph E. Sutaris Name: Joseph E. Sutaris Title: Executive Vice President an…

Chief Accounting Officer — Deresa F. Durkee: The filing discloses the internal promotion of an existing employee to the role of Chief Accounting Officer, which is a standard succession or role expansion event rather than a departure.

Director — Savneet Singh: The filing discloses the election of a new independent director to the board, which is a routine governance event and not a departure of a senior executive.

above. 99.1 Press Release, dated July 23, 2024, issued by Community Financial System, Inc. 104 Cover Page Interactive Data File (embedded in the cover page formatted in Inline XBRL) SIGNATURES Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. Community Financial System, Inc. By: /s/ Joseph E. Sutaris Name: Joseph E. Sutaris Title: Executive Vice President and C…

Other Events. On July 17, 2024, the Company issued a press release announcing the approval by the Board of an increase to the Company’s regular quarterly dividend to $0.46 per share payable on October 10, 2024, to Shareholders of record as of September 13, 2024. The foregoing descriptions are summaries of the Amendment, the Executive Severance Plan, the Code, and Press Release and are qualified in their entirety by reference to the full text of the Press Release and agreement, copies of which…