19 C.F.R. § 145.23
A mail entry made before December 18, 2004 may be amended under section 520(c), Tariff Act of 1930, as amended (19 U.S.C. 1520(c) ), only if the addressee requests such amendment within the time limits prescribed therein (see §§ 173.4 and 173.5 of this chapter), and the claim is allowable under section 520(c). Requests for adjustment in the amount of duty assessed under mail entries made under § 145.22(a) must be made in such time that the request can be acted upon by the port director within 90 days after receipt of the mail article and payment of the duties by the addressee. For a mail entry made before December 18, 2004, protests under § 145.22(c) of this chapter must be filed no later than 90 days after payment of the duties by the addressee, but may be acted upon by CBP after expiration of that 90-day period. For a mail entry made on or after December 18, 2004, protests under § 145.22(c) of this chapter must be filed no later than 180 days after payment of the duties by the addressee, but may be acted upon by CBP after expiration of that 180-day period.
19 C.F.R. §145.23