19 CFR § 141.51
Quantity usually required to be in one entry
July 16, 2020
All merchandise arriving on one conveyance and consigned to one consignee must be included on one entry, except as provided in §141.52. In addition, a shipment of merchandise that arrives by separate conveyances at the same port of entry in multiple portions, either as a shipment split by the carrier or as components of a large unassembled or disassembled entity, may be processed under a single entry, as prescribed, respectively, in §§141.57 and 141.58.
[CBP Dec. 06-11, 71 FR 31925, June 2, 2006]