Sec Form 4 Filing - ACE BRIAN R @ COMMUNITY BANK SYSTEM, INC. - 2020-03-17

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL OMB Number: 3235-0287 Expires: November 30, 2011 Estimated average burden hours per response... 0.5

1. Name and Address of Reporting Person ACE BRIAN R 2. Issuer Name and Ticker or Trading Symbol COMMUNITY BANK SYSTEM, INC. [ CBU] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director _____ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O COMMUNITY BANK SYSTEM, INC., 5790 WIDEWATERS PARKWAY 3. Date of Earliest Transaction (MM/DD/YY) 03/17/2020 (Street) DEWITT, NY13214 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 60,773 ( 1 ) D Common Stock 144 ( 2 ) I By Spouse

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Phantom Stock (Deferred Stock Units) ( 3 ) 03/17/2020 A 667 ( 3 ) ( 3 ) Common Stock 667 $ 0 4,405.826 ( 4 ) D Phantom Stock (Deferred Compensation) ( 5 ) ( 5 ) ( 5 ) Common Stock 12,453.5955 12,453.5955 ( 6 ) D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other ACE BRIAN R C/O COMMUNITY BANK SYSTEM, INC. 5790 WIDEWATERS PARKWAY DEWITT, NY13214 X Signatures /s/ Danielle M. Cima, pursuant to a Confirming Statement executed by Brian R. Ace 03/19/2020 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Includes 630.084 shares acquired pursuant to the Community Bank System, Inc. Dividend Reinvestment Plan. ( 2 )Includes four shares acquired pursuant to the Community Bank System, Inc. Dividend Reinvestment Plan. ( 3 )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. ( 4 )Includes 21.5956 units of phantom stock acquired on January 10, 2020 as dividend equivalents under the 2014 Long-Term Incentive Compensation Program. ( 5 )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. ( 6 )Includes 86.5955 units of phantom stock acquired on January 10, 2020 under the Deferred Compensation Plan's dividend reinvestment feature.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.