19 USC 1520 - Refunds and errors

(a) Cases in which refunds authorized 
The Secretary of the Treasury is authorized to refund duties or other receipts in the following cases:
(1) Excess deposits.— 
Whenever it is ascertained on liquidation or reliquidation of an entry or reconciliation that more money has been deposited or paid as duties than was required by law to be so deposited or paid.
(2) Fees, charges, and exactions.— 
Whenever it is determined in the manner required by law that any fees, charges, or exactions, other than duties and taxes, have been erroneously or excessively collected.
(3) Fines, penalties, and forfeitures.— 
Whenever money has been deposited in the Treasury on account of a fine, penalty, or forfeiture which did not accrue, or which is finally determined to have accrued in an amount less than that so deposited, or which is mitigated to an amount less than that so deposited or is remitted.
(4) Prior to liquidation.— 
Prior to the liquidation of an entry or reconciliation, whenever an importer of record declares or it is ascertained that excess duties, fees, charges, or exactions have been deposited or paid.
(b) Authorization of appropriations 
The necessary moneys to make such refunds are authorized to be appropriated annually from the general fund of the Treasury.
(c) Repealed. Pub. L. 108–429, title II, § 2105, Dec. 3, 2004, 118 Stat. 2598 
(d) Goods qualifying under free trade agreement rules of origin 
Notwithstanding the fact that a valid protest was not filed, the Customs Service may, in accordance with regulations prescribed by the Secretary, reliquidate an entry to refund any excess duties (including any merchandise processing fees) paid on a good qualifying under the rules of origin set out in section 3332 of this title, section 202 of the United States-Chile Free Trade Agreement Implementation Act, section 4033 of this title, section 202 of the United States-Oman Free Trade Agreement Implementation Act, or section 203 of the United States-Peru Trade Promotion Agreement Implementation Act for which no claim for preferential tariff treatment was made at the time of importation if the importer, within 1 year after the date of importation, files, in accordance with those regulations, a claim that includes
(1) a written declaration that the good qualified under the applicable rules at the time of importation;
(2) copies of all applicable NAFTA Certificates of Origin (as defined in section 1508 (b)(1) of this title), or other certificates or certifications of origin, as the case may be; and
(3) such other documentation and information relating to the importation of the goods as the Customs Service may require.