Initial Statement of Beneficial Ownership (3)

FORM 3	UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES	OMB APPROVAL OMB Number: 3235-0104 Estimated average burden hours per response... 0.5
	Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940

1. Name and Address of Reporting Person * Herning Andrew J	2. Date of Event Requiring Statement (MM/DD/YYYY) 1/12/2021	3. Issuer Name and Ticker or Trading Symbol BTRS Holdings Inc. [BTRS]
(Last)        (First)        (Middle) C/O BTRS HOLDINGS INC., 1009 LENOX DRIVE, SUITE 101	4. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director                          _____ 10% Owner ___X___ Officer (give title below)        _____ Other (specify below) Senior Vice President, Finance /
(Street) LAWRENCEVILLE, NJ 08648       (City)              (State)              (Zip)	5. If Amendment, Date Original Filed(MM/DD/YYYY)	6. Individual or Joint/Group Filing(Check Applicable Line) _X_ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Beneficially Owned
1.Title of Security (Instr. 4)	2. Amount of Securities Beneficially Owned (Instr. 4)	3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	4. Nature of Indirect Beneficial Ownership (Instr. 5)
Class 1 Common Stock	16034 (1)(2)	D

Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivate Security (Instr. 4)	2. Date Exercisable and Expiration Date (MM/DD/YYYY)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Stock Option (right to buy)	(3)	12/15/2025	Class 1 Common Stock	130108	$1.77	D
Stock Option (right to buy)	(4)	5/11/2030	Class 1 Common Stock	72282	$2.19	D
Stock Option (right to buy)	(5)	5/11/2030	Class 1 Common Stock	7914	$2.19	D
Stock Option (right to buy)	(3)	1/10/2031	Class 1 Common Stock	83125	$15.71	D

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) 14,456 shares of the Issuer's Class 1 Common Stock, par value $0.0001 per share (the "Shares") in exchange for 2,000 shares of the common stock of Former Billtrust held directly by the reporting person; (ii) 789 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) 789 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)	Immediately exercisable.
(4)	The shares underlying this option shall vest and become exercisable in 8 equal semi-annual installments beginning on November 12, 2020, subject to the Reporting Person's continuous service with the Issuer on each such date.
(5)	The shares underlying this option shall vest and become exercisable in 4 equal semi-annual installments beginning on November 12, 2020, subject to the Reporting Person's continuous service with the Issuer on each such date.

Remarks: Exhibit List - Exhibit 24 - Power of Attorney

Reporting Owners
Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
Herning Andrew J C/O BTRS HOLDINGS INC. 1009 LENOX DRIVE, SUITE 101 LAWRENCEVILLE, NJ 08648			Senior Vice President, Finance

Signatures
/s/ Asher Herzog, Attorney-in-Fact		2/9/2021
**Signature of Reporting Person		Date