504 Credit Risk Management Improvement Act of 2021 This bill revises the duties of the Office of Credit Risk Management to include oversight of a certified development company (CDC) that participates in the 504 Loan Program of the Small Business Administration (SBA), and it requires the SBA to issue rules related to certain environmental requirements. The 504 Loan Program provides a small business with SBA financing—through a CDC intermediary—for expansion or modernization. Specifically, the bill requires the office to oversee any CDC that participates in the program and to conduct file reviews with respect to loan closings under the program. Further, the bill authorizes the office to take formal and informal enforcement actions against a CDC for specified violations and to charge each CDC a fee. The SBA must issue rules to clarify the procedures necessary for an eligible CDC to comply with certain environmental requirements.