Application Identifier (AI) 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 forms the first digits of the GCN and ensures its global uniqueness. The structure and content of the GCN are determined by the owner of the GS1 Company Prefix and are used to uniquely identify each coupon offer. The digit preceding the optional serial number is a check digit.
The optional serial number is assigned to each individual coupon, and its structure is determined by the coupon issuer. The combination of the GS1 Company Prefix, the coupon reference number, and the serial number uniquely identifies each coupon. The serial number is numeric and may contain up to 12 digits.