X0306 4 2020-03-17 0000723188 COMMUNITY BANK SYSTEM, INC. CBU 0001264817 ACE BRIAN R C/O COMMUNITY BANK SYSTEM, INC. 5790 WIDEWATERS PARKWAY DEWITT NY 13214 1 Common Stock 60773 D Common Stock 144 I By Spouse Phantom Stock (Deferred Stock Units) 2020-03-17 4 A 0 667 0 A Common Stock 667 4405.826 D Phantom Stock (Deferred Compensation) Common Stock 12453.5955 12453.5955 D Includes 630.084 shares acquired pursuant to the Community Bank System, Inc. Dividend Reinvestment Plan. Includes four shares acquired pursuant to the Community Bank System, Inc. Dividend Reinvestment Plan. The reporting person has received deferred stock units under the Community Bank System, Inc. 2014 Long-Term Incentive Plan. Each phantom stock unit which represents a deferred stock unit is the economic equivalent of one share of Community Bank System, Inc. common stock and will be settled in common stock at a predetermined date. Includes 21.5956 units of phantom stock acquired on January 10, 2020 as dividend equivalents under the 2014 Long-Term Incentive Compensation Program. Each unit of phantom stock is the economic equivalent of one share of Community Bank System, Inc. common stock. The units of phantom stock relating to the Deferred Compensation Plan will be settled in Community Bank System, Inc. common stock at future dates selected by the reporting person. Includes 86.5955 units of phantom stock acquired on January 10, 2020 under the Deferred Compensation Plan's dividend reinvestment feature. /s/ Danielle M. Cima, pursuant to a Confirming Statement executed by Brian R. Ace 2020-03-19