The most common use of a GS1 prefix is as a basis for assigning UPCs to products, however, GS1 prefixes are also used in EDI. The main function it serves for EDI is as a basis for assigning a unique Serial Shipping Container Code (also known as SSCC18) number to the GS1-128 carton labels you must affix to each of your cartons when shipping as an EDI compliant vendor.