Small-Dollar PPP Forgiveness Simplification Act of 2021 This bill makes changes to the Paycheck Protection Program (PPP) to with respect to forgiveness of certain PPP loans. Specifically, the bill includes as covered loans under the PPP loan forgiveness program excess loan amounts that were received due to a good faith error. The bill also increases the threshold, from $150,000 to $350,000, used to determine whether a PPP loan may use the simplified forgiveness application.