Identify coupons with a GCN A Global Coupon Number (GCN) is used to uniquely and unambiguously identify a coupon. GS1 Company Prefix (54 M1 M2 ...) and coupon number (X1 X2 ...) Check digit 5 4 M1 M2 M3 M4 M5 X1 X2 X3 X4 X5 C 5 4 M1 M2 M3 M4 M5 M6 X1 X2 X3 X4 5 4 M1 M2 M3 M4 M5 M6 M7 X1 X2 X3 5 4 M1 M2 M3 M4 M5 M6 M7 M8 X1 X2 5 4 M1 M2 M3 M4 M5 M6 M7 M8 M9 X1 Please note: a GCN can only be created through a platform, you can therefore not do it yourself. You can create your GCNs through My Coupon Manager. The GCN is encoded in either a GS1 DataBar Expanded or GS1 DataBar Expanded Stacked barcode type. Members of GS1 Belgium & Luxembourg are granted access to the Coupon Barcode Creator for this.