X0508 4 2025-04-14 0000723188 COMMUNITY FINANCIAL SYSTEM, INC. CBU 0001900543 Knauss Jeffery J C/O COMMUNITY FINANCIAL SYSTEM, INC. 5790 WIDEWATERS PARKWAY DEWITT NY 13214 1 0 Common Stock 2025-04-14 4 M 0 12 0 A 3566.4908 D Phantom Stock (Deferred Stock Units) 2025-04-14 4 M 0 12 0 D Common Stock 12 1225 D On April 14, 2025, the reporting person's phantom stock units were settled for 12 shares of Community Financial System, Inc. common stock, and .7836 shares were settled in cash at the price of $51.47 per share. The reporting person has received deferred stock units under the Community Financial System, Inc. 2022 Long-Term Incentive Plan, as amended (the "Plan"). Each phantom stock unit which represents a deferred stock unit is the economic equivalent of one share of Community Financial System, Inc. common stock and will be settled in common stock at a predetermined date. Includes 12.7836 units of phantom stock acquired on April 10, 2025 under the Plan's dividend reinvestment feature. /s/ Danielle M. Cima, pursuant to a Confirming Statement executed by Jeffery J. Knauss 2025-04-16