The Importer Security Filing (ISF) must be revised if there is a change in information or if more accurate information becomes available before the goods arrive at the first port of entry in the United States.

If the flexible filing option (FR, FT, or FX) is used, the ISF must be updated with the correct or more accurate information as soon as it is known, but no later than 24 hours before the vessel’s arrival at the first U.S. port. If the original information is the most accurate available, the ISF must still be completed using the CT amendment code.