31 U.S.C. § 3323

1. (a)Except as provided in section 3326 of this title, the Secretary of the Treasury may pay out money only against a warrant. A warrant shall be—
   1. (1)authorized by law;
   2. (2)signed by the Secretary; and
   3. (3)countersigned by the Comptroller General.
2. (b)
   1. (1)A disbursing official shall send to the Secretary with a warrant a certificate under section 3526 of this title, or a requisition for an advance. The certificate or requisition shall state the appropriation to which the payment is to be charged.
   2. (2)The Secretary shall return the certificate or requisition to the Comptroller General with the date and amount endorsed on the certificate or requisition.
3. (c)A requisition for the payment of money on an audited account or for depositing money in the Treasury is not required.
4. (d)The Secretary and the Comptroller General shall charge to the appropriate appropriation in their books any money paid by a warrant.