ISF has to be filed at least 24 hours before an ocean shipment loads at the foreign port, not before it reaches the US. Miss it and CBP can assess liquidated damages per violation on top of any duty owed.
Why it’s called 10+2
Ten elements are the importer’s responsibility to file, usually through a customs broker. Two more (vessel stow plan and container status) come from the ocean carrier, not the importer. Only the 10 importer elements are listed as action items above, the carrier elements happen automatically on their end once booking is confirmed.
The 24-hour rule is before loading, not before arrival
This is the detail that trips up first-time importers. “24 hours before loading” means before the container is loaded onto the vessel at the foreign port of export, which can be weeks before the ship actually reaches a US port. If your supplier books the vessel with short notice, your ISF window can be tighter than it looks on a shipping calendar.
What happens if ISF is late or wrong
CBP can hold the shipment at the port, assess liquidated damages (commonly $5,000 per violation, with potential for multiple violations per shipment), and flag the importer for increased scrutiny on future entries. None of that is worth the admin shortcut of filing late.
Once ISF is filed, move to the import customs clearance checklist for what happens at arrival.