X0508 4/A 2024-11-07 2024-11-07 0000723188 COMMUNITY FINANCIAL SYSTEM, INC. CBU 0001608689 Durkee Deresa Fischer C/O COMMUNITY FINANCIAL SYSTEM, INC. 5790 WIDEWATERS PARKWAY DEWITT NY 13214 1 SVP, Chief Accounting Officer 0 Common Stock 2024-11-07 4 M 0 427 38.02 A 4986.604 D Common Stock 2024-11-07 4 M 0 1705 51.64 A 6691.604 D Common Stock 2024-11-07 4 F 0 1711 70.79 D 4980.604 D Common Stock 91.666 I By 401(k) Common Stock 218 I By spouse Stock Option 38.02 2024-11-07 4 M 0 427 0 D 2026-03-16 Common Stock 427 0 D Stock Option 51.64 2024-11-07 4 M 0 1705 0 D 2030-03-17 Common Stock 1705 427 D Due to an administrative error, the Reporting Person is filing this amendment to correct the date of the transaction to November 7, 2024 and update the price of the Community Financial System, Inc. common stock used for the settlement of shares to cover the exercise price and the taxes associated with this stock option exercise. The number of shares tendered to cover the exercise price and taxes has been reduced from 1,841 shares to 1,711 shares. The option vested ratably on March 16, 2017, 2018, 2019, 2020, and 2021. The option vests ratably on March 17, 2021, 2022, 2023, 2024, and 2025. /s/ Danielle M. Cima, pursuant to a Confirming Statement executed by Deresa F. Durkee 2024-11-15