31 U.S.C. § 3727: Assignments of claims

a transfer or assignment of any part of a claim against the United States Government or of an interest in the claim; or the authorization to receive payment for any part of the claim. An assignment may be made only after a claim is allowed, the amount of the claim is decided, and a warrant for payment of the claim has been issued. The assignment shall specify the warrant, must be made freely, and must be attested to by 2 witnesses. The person making the assignment shall acknowledge it before an official who may acknowledge a deed, and the official shall certify the assignment. The certificate shall state that the official completely explained the assignment when it was acknowledged. An assignment under this subsection is valid for any purpose. the contract does not forbid an assignment; is for the entire amount not already paid; is made to only one party, except that it may be made to a party as agent or trustee for more than one party participating in the financing; and may not be reassigned; and the assignee files a written notice of the assignment and a copy of the assignment with the contracting official or the head of the agency, the surety on a bond on the contract, and any disbursing official for the contract. to the Government independent of the contract; or because of renegotiation, fine, penalty (except an amount that may be collected or withheld under, or because the assignor does not comply with, the contract), taxes, social security contributions, or withholding or failing to withhold taxes or social security contributions, arising from, or independent of, the contract. An assignee under this section does not have to make restitution of, refund, or repay the amount received because of the liability of the assignor to the Government that arises from or is independent of the contract. The Government may not collect or reclaim money paid to a person receiving an amount under an assignment or allotment of pay or allowances authorized by law when liability may exist because of the death of the person making the assignment or allotment.