Sec Form 3 Filing - Lane Flint A. @ BTRS Holdings Inc. - 2021-01-12

FORM 3 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

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1. Name and Address of Reporting Person Lane Flint A. 2. Issuer Name and Ticker or Trading Symbol BTRS Holdings Inc. [ BTRS] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director X __ 10% Owner X __ Officer (give title below) _____ Other (specify below) Chief Executive Officer (Last) (First) (Middle) C/O BTRS HOLDINGS INC., 1009 LENOX DRIVE, SUITE 101 3. Date of Earliest Transaction (MM/DD/YY) 01/12/2021 (Street) LAWRENCEVILLE, NJ08648 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 Class 1 Common Stock 17,469,145 ( 1 ) ( 2 ) D Class 1 Common Stock 7,839,464 ( 3 ) I By GRAT ( 4 )

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 Stock Option (right to buy) $ 0.49 ( 5 ) 04/30/2023 Class 1 Common Stock 180,706 D Stock Option (right to buy) $ 1.27 ( 5 ) 01/31/2025 Class 1 Common Stock 62,647 D Stock Option (right to buy) $ 1.88 ( 5 ) 01/30/2027 Class 1 Common Stock 89,146 D Stock Option (right to buy) $ 1.93 ( 6 ) 05/14/2027 Class 1 Common Stock 361,413 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Lane Flint A. C/O BTRS HOLDINGS INC. 1009 LENOX DRIVE, SUITE 101 LAWRENCEVILLE, NJ08648 X X Chief Executive Officer Signatures /s/ Asher Herzog, Attorney-in-Fact 01/21/2021 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Received on January 12, 2021 pursuant to the Business Combination Agreement, dated as of October 18, 2020, by and among South Mountain Merger Corp. ("South Mountain" and, upon consummation of the business combination, the surviving Issuer as renamed BTRS Holdings Inc.), Factor Systems, Inc. (d/b/a Billtrust), a Delaware corporation ("Former Billtrust"), BT Merger Sub I, Inc., a Delaware corporation and a direct, wholly owned subsidiary of South Mountain, and BT Merger Sub II, LLC, a Delaware limited liability company and a direct, wholly owned subsidiary of South Mountain (as amended by Amendment No. 1, dated as of December 13, 2020). ( 2 )Included are (i) 15,750,081 shares of the Issuer's Class 1 Common Stock, par value $0.0001 per share (the "Shares") in exchange for 2,492,170 shares of the common stock of Former Billtrust held directly by the reporting person; (ii) 859,532 Shares to be received directly by the reporting person if the Issuer's closing share price equals or exceeds $12.50 for any 20 trading days within any consecutive 30-trading day period prior to January 12, 2026; and (iii) 859,532 Shares to be received directly by the reporting person if the Issuer's closing share price equals or exceeds $15.00 for any 20 trading days within any consecutive 30-trading day period prior to January 12, 2026. ( 3 )Included are (i) 7,068,016 Shares in exchange for 977,830 shares of the common stock of Former Billtrust held by the Flint Lane 2009 Grantor Retained Annuity Trust (the "GRAT"); (ii) 385,724 Shares to be received by the GRAT if the Issuer's closing share price equals or exceeds $12.50 for any 20 trading days within any consecutive 30-trading day period prior to January 12, 2026; and (iii) 385,724 Shares to be received by the GRAT if the Issuer's closing share price equals or exceeds $15.00 for any 20 trading days within any consecutive 30-trading day period prior to January 12, 2026. ( 4 )These Shares are held by the Flint Lane 2009 Grantor Retained Annuity Trust (the "GRAT") for the benefit of the Reporting Person's children. The Reporting Person's spouse is trustee of the GRAT. The Reporting Person disclaims beneficial ownership of these securities, and the filing of this report is not an admission that the Reporting Person is the beneficial owner of these securities for purposes of Section 16 or for any other purpose. ( 5 )Immediately exercisable. ( 6 )The Shares underlying this option shall vest and become exercisable in 8 equal semi-annual installments beginning on November 15, 2017, subject to the Reporting Person's continuous service with the Issuer on each such date.

Remarks: Exhibit List - Exhibit 24 - Power of Attorney

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