Application Identifier 255 contains a Global Coupon Number (GCN). The GCN provides a globally unique identification for a coupon with an optional serial number.
The GS1 Company Prefix is the first digits of the GCN, making the GCN globally unique. The structure and content of the GCN is determined by the owner of the GS1 Company Prefix and is used to uniquely identify each coupon type. The digit before the optional serial number is a check digit.
The optional serial number is assigned to each coupon, and the structure is determined by the coupon issuer. The combination of GS1 Enterprise Prefix, coupon reference number, and serial number uniquely identifies each coupon. The serial number is numeric and can contain up to 12 digits.