19 CFR § 142.2 - Time for filing entry.
(a) General rule: After arrival of merchandise. Merchandise for which entry is required will be entered within 15 calendar days after landing from a vessel, aircraft or vehicle, or after arrival at the port of destination in the case of merchandise transported in bond.
(b) Before arrival of merchandise -
(1) Entry. The entry documentation required by § 142.3(a) may be submitted before the merchandise arrives within the limits of the port where entry is to be made, in which case the time of entry shall be the time specified in § 141.68(a).
(2) When entry summary serves as entry. The entry summary when it will be filed at time of entry to serve as both the entry and the entry summary, as provided in § 142.3(b), may be submitted for preliminary review in accordance with §§ 141.63(a) and 142.12(a)(2).