Master bills, house bills and who files them
The vessel operating carrier reports the master Bill of Lading for each shipment it carries. When an NVOCC is involved, its house bills must be reported too. An NVOCC licensed by or registered with the FMC and holding an international carrier bond can transmit its house bill data directly to CBP. Otherwise it must give the data to the vessel carrier, which presents it. Either way, house and master bills must link correctly, because later holds and releases are posted against them.
Why manifest data is due before loading
The 24-hour rule gives CBP time to screen U.S.-bound containers for security risks before they leave the foreign port. Carriers set their documentation cut-offs ahead of departure partly so they can file on time, which is why late shipping instructions can cost a sailing. CBP now handles ocean manifests within its Automated Commercial Environment, but the trade still calls the filing AMS.
Manifest data in the arrival and release chain
After arrival, the manifest becomes the reference for everything that follows. The customs entry cites the Bill of Lading numbers, and in-bond moves and general order notices tie back to the same bills. A typo in a B/L number or a missing house bill can leave a container with no release on file even after the broker has filed. When a release seems to be missing, check the manifest first.
Example
An NVOCC with its own SCAC files the house bill for HLBU2456904 in AMS while the ocean carrier files the master bill, and the broker's entry later cites both numbers.
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Official sources
Questions
What does AMS (Automated Manifest System) mean?
AMS, the Automated Manifest System, is the CBP system carriers use to file inbound cargo manifest data for U.S.-bound shipments. For ocean cargo, the carrier's electronic cargo declaration is generally due 24 hours before the cargo is loaded at the foreign port.
What is the difference between AMS and ISF?
AMS carries the carrier's manifest data: which bills, which containers and which vessel. The ISF carries the importer's commercial and supply chain data. CBP uses both for screening, and they need to line up at the Bill of Lading level.
Does the 24-hour rule apply to bulk cargo?
Not in the same way. Bulk cargo, and break bulk cargo with an approved exemption, can be declared 24 hours before the vessel arrives in the U.S. instead of before loading. Containerized cargo always follows the pre-loading deadline.