Small Business Mergers, Acquisitions, Sales, and Brokerage Simplification Act of 2021 This bill exempts from securities registration requirements certain merger-and-acquisition brokers that facilitate transfer of ownership in privately held companies with earnings or revenues under a specified threshold. However, this exemption shall not apply to certain brokers, including those that provide financing related to the transfer of ownership, engage on behalf of any party in a transaction involving specified shell companies, or have been barred or suspended from association with a broker or dealer.