BTRS Holdings Inc., formerly South Mountain Merger Corp (Nasdaq: SMMC), was a blank-check company that completed its initial public offering in 2020 with a focus on the financial technology sector. Sponsored by South Mountain Merger Partners LLC, SMMC pursued a business combination with Billtrust, a provider of B2B accounts receivable automation and payment solutions. The S-1 registration statement filed with the SEC on February 3, 2021 relates to the post-combination entity, BTRS Holdings Inc., following the deal's close in January 2021, after which the company traded under the ticker BTRS on Nasdaq. The combined entity operates in the B2B payments and order-to-cash automation space. Sign up at SpacDesk for full filings, timeline data, and analytics on this and hundreds of other SPAC transactions.