19 CFR § 141.1 - Liability of importer for duties.
(a) Time duties accrue. Duties and the liability for their payment accrue upon imported merchandise on arrival of the importing vessel within a Customs port with the intent then and there to unlade, or at the time of arrival within the Customs territory of the United States if the merchandise arrives otherwise than by vessel, unless otherwise specially provided for by law.
(b) Payment of duties -
(1) Personal debt of importer. The liability for duties, both regular and additional, attaching on importation, constitutes a personal debt due from the importer to the United States which can be discharged only by payment in full of all duties legally accruing, unless relieved by law or regulation. Payment to a broker covering duties does not relieve the importer of liability if the duties are not paid by the broker. The liability may be enforced notwithstanding the fact that an erroneous construction of law or regulation may have enabled the importer to pass his goods through the customhouse without payment. Delivery of a Customs bond with an entry is solely to protect the revenue of the United States and does not relieve the importer of liabilities incurred from the importation of merchandise into the United States.
(2) Means of payment. An importer or his agent may pay Customs by using any of the applicable means provided in § 24.1(a).
(3) Methods of payment. An importer may pay duties either:
(i) Directly to Customs whether or not a licensed customhouse broker is used; or
(ii) Through a licensed customhouse broker. When an importer uses a broker and elects to pay by check or bank draft, the importer may issue the broker either:
(A) One check or bank draft payable to the broker covering both duties and the broker's fees and charges, in which case the broker shall pay the duties to Customs on behalf of the importer, or
(B) Separate checks or bank drafts, one covering duties payable to the “U.S. Customs Service,” for transmittal by the broker to Customs, and the other covering the broker's fees and charges. The importer's check or bank draft for duties shall be delivered to Customs by the broker.
(c) Claim against estate of importer. The claim of the Government for unpaid duties against the estate of a deceased or insolvent importer has priority over obligations to creditors other than the United States. To the extent that a broker or a surety pays duties on behalf of an importer which files for bankruptcy protection, the broker or surety shall be entitled to assume the priority status of Customs under section 507(a)(7) of the Bankruptcy Code for that portion of Customs claim which the surety or broker has paid.
(d) Lien against merchandise. The liability for duties also constitutes a lien upon the merchandise imported which may be enforced while such merchandise is in the custody or subject to the control of the United States.
(e) States and their instrumentalities. Neither the States nor their instrumentalities are entitled to any constitutional exemption from the payment of Customs duties.
(f) Unordered merchandise. There shall be no liability for the payment of duties on the part of anyone to whom merchandise is consigned without his authority, if he refuses it. Such merchandise shall be treated as unclaimed (see part 27 of this chapter).