GS1 and GTIN (product and logistics numbering)
GS1 runs a global numbering system that identifies products, logistic units and locations: GTIN on the product, SSCC on the pallet, GLN on the delivery point. The number is unique worldwide, so the same product means the same thing at the manufacturer, at the wholesaler and at the retail chain.
A GTIN is the number encoded under the EAN-13 barcode on a consumer unit. A case and a pallet carry their own numbers, different from the single unit, which is what lets a system tell a twelve-pack from one piece. In Poland the number ranges are issued by GS1 Polska, and the number is assigned by the manufacturer or importer, not by the wholesaler reselling the goods.
An SSCC identifies one specific logistic unit, that single pallet, rather than a type of product. It is printed on the logistic label in a GS1-128 barcode together with application identifiers such as batch number, best-before date and quantity. Scanning one label then tells the warehouse and the buyer exactly what stands on the pallet.
The same numbers tie EDI to the warehouse. In a DESADV message the supplier lists the SSCCs of the pallets being shipped, and the buyer scans the label at the dock and receives the whole pallet in one move instead of counting cartons. If the label does not match the message, goods-in stops.
You can spot the problem in your own company: the same product sits under two item codes, pallet labels are printed from Word with the number typed by hand, and barcodes for new deliveries are written on a sheet of paper by a warehouse worker. Scanning will not work whatever system sits above the warehouse.