Once the goods enter the US territory, they are not considered officially entered until they have been permitted by CBP (Customs & Border Protection) and duties have been paid. The products must be declared within 15 days of their arrival within the country or within 15 days of their departure from the bonded warehouse. If you are an importer, you must declare the transaction value of your products, as well as the country of origin (and other documents: please see below). The duties will then be calculated by CBP.