19 C.F.R. § 190.38 – Recordkeeping.

(a) Maintained by claimant; by others. Pursuant to 19 U.S.C. 1508(c)(3), all records which are necessary to be maintained by the claimant under this part with respect to drawback claims, and records kept by others to complement the records of the claimant, which are essential to establish compliance with the legal requirements of 19 U.S.C. 1313(j)(1) or (j)(2), as applicable, and this part with respect to drawback claims, must be retained for 3 years after liquidation of such claims (under 19 U.S.C. 1508, the same records may be subject to a different retention period for different purposes).
(b) Accounting for the merchandise. Merchandise subject to drawback under 19 U.S.C. 1313(j)(1) and (j)(2) must be accounted for in a manner which will enable the claimant:
1. (1) To determine, and CBP to verify, the applicable import entry or transfer(s) of drawback-eligible merchandise;
2. (2) To determine, and CBP to verify, the applicable exportation or destruction; and
3. (3) To identify, with respect to the import entry or any transfer(s) of drawback-eligible merchandise, the imported merchandise designated as the basis for the drawback claim.