Customs and Border Protection (CBP) is a federal law enforcement agency under the United States Department of Homeland Security (DHS). CBP has a dual mission of protecting the United States from terrorism and other threats, and facilitating lawful trade and travel.
Some of the specific things that CBP does includes:
Anyone importing products into the United States, whether for domestic distribution or as part of an import for re-export, must work with the CBP. Failing to meet necessary regulations can result in various fines and penalties against the importer.
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ISF Filing: Requirements and How to Submit to CBP
The Complete Beginners Guide to Importing and Exporting – USA Customs Clearance