Field guides / 04

Warehouse and E-Commerce Labels: Internal SKUs, FNSKUs and GS1 Codes

A shirt can carry three identifiers: your own SKU, the product GTIN, and a fulfillment identifier. Decide who owns the lookup table before deciding which number to print.

1 · Internal inventory: you control the lookup

For a closed warehouse system, define a unique key and map it to an item or location. Use TSHIRT-NVY-L for a variant, RACK04-SHELF2-B for a bin, or LOT-202611-0089 for a batch. A batch number alone does not identify every individual unit.

To test the workflow, create the bin record first, encode its exact key with Code 128, and scan the printed label into the location field. A successful scan should select the intended bin without a manual search. Manage duplicate keys and retired labels in your own system.

2 · Retail distribution: use the assigned GTIN

For an existing branded product, start with the identifier on the packaging or confirm it with the brand owner. For a new product you own, follow GS1 allocation guidance and your trading partner’s listing requirements. Some marketplace listings may qualify for a GTIN exemption; do not invent a number simply to fill in the field.

A barcode generator draws the symbol for an identifier. It does not assign a GTIN or establish ownership. Check the item and package level, then use Verified by GS1 to look up available registration information. A valid checksum alone cannot tell a single unit from a case.

3 · Fulfillment by Amazon: use shipment instructions

An FNSKU is an Amazon fulfillment identifier, distinct from both your internal SKU and the retail GTIN. Check the barcode instructions in Seller Central for the actual listing, marketplace and shipment. When an Amazon barcode is required, use the item label supplied for that offer. Do not fabricate an FNSKU, infer it from a prefix or substitute a generic Code 128 image for the prescribed label.

Match the label to the correct variant and condition. Follow the shipment-specific directions on placement and which other barcodes to cover; do not obscure required serial, safety or other markings. Keep item labels distinct from shipping-box labels.

Reference: Amazon · Product IDs and GTINs