19 C.F.R. § 161.5
(b) Deposit of specific sum tendered. No offer in which a specific sum of money is tendered in compromise of a Government claim under the Customs laws will be considered by the Commissioner of Customs until due notice is received that such sum has been properly deposited in the name of the person submitting the offer with the Treasurer of the United States or a Federal Reserve bank. A proponent at a distance from a Federal Reserve bank may perfect his offer by tendering a bank draft for the amount of the offer payable to the Secretary of the Treasury for collection and deposit. If the offer is rejected, the money will be returned to the proponent.
(Sec. 617, 46 Stat. 757, as amended; 19 U.S.C. 1617)