31 U.S.C. § 3305: Audits of depositaries

The Secretary of the Treasury, or an officer, employee, or agent designated by the Secretary, may audit a depositary of public money. For uniformity and accuracy in accounts and safety of public money, an individual conducting an audit shall audit a depositary’s—(1) books; (2) accounts; (3) returns; and (4) public money on hand and the way the money is kept.