The date of exportation of your product determines the applicable rate . You have to show proof to customs. However, once you applied and received the letter from Customs, you have to apply it. Common pitfalls of the first time importer are a lack of direct control over the process and a lack of understanding of quotas and visas. A company can bring goods into the FTZ without having to pay a duty.
Goods are dutiable only when they leave the free trade zone and enter the United States.
Customs permits this as long as the facilities importing the products have decent security, a sufficient inventory system, and have a bond in place. Foreign trade zones are located throughout the country and each is assigned a number. Baltimore's trade zone number is 74. A subzone is a special purpose zone established as an adjunct to an existing FTZ for a limited purpose that cannot be accommodated within an existing zone. A subzone is 74A - Baltimore Marine Industries.