You have to map all foreign-trade zones relevant to your imports as customs IDs in both the feeder system and the SAP GTS system. The customs ID is the reference level of inventory management in SAP GTS. Receipts to and issues from a foreign-trade zone are recorded for the customs ID representing the zone in the system. You define customs IDs in Customizing and add basic data like the ID and the Facilities Information and Resources Management System (FIRMS) code of the location within the foreign-trade zone to be mapped.
In the feeder system, you assign at least one combination of plant and storage location to a customs ID representing a foreign-trade zone. Only procurement processes that are based on the plant/storage location combinations assigned to a customs ID for a foreign-trade zone can be transferred to the work-lists for admission to that zone in SAP GTS.

All products to be introduced into a foreign-trade zone in SAP GTS have to be flagged as relevant for the procedure on the Special Customs Procedures tab in the product master. You further have to specify on this tab whether the product is a finished product or a component. If the product is a finished product that is to be manufactured in the foreign-trade zone, add a BOM on the Bill of Material tab to specify the proportion of quantities of components to product.
If you usually apply for the privileged foreign status for the imported goods that you transfer to a foreign-trade zone, you can select the corresponding indicator in the Zone Status field on the Special Customs Procedures tab. However, the system also provides an indicator for merchandise with non-privileged foreign status.
Once you have maintained the product master, you send this information to the feeder system using the Redistribution: Products for Special Customs Procedures - Individual or Redistribution: Products for Special Customs Procedures - Mass Proc. transactions (transaction codes /SAPSLL/PR_DISTR_SG and /SAPSLL/PR_DISTR_MS respectively). There is also an app for the individual transfer of information regarding special procedures (Distribute Product Data to Feeder System - Special Procedure).
Note
The information on foreign-trade zone relevance is stored in the /SAPSLL/ECPPA table in the feeder system’s database.