Amazon uses several identifiers for every product, and mixing them up is one of the most common causes of shipment problems. Here's what each one does, and what changed in 2026.
The identifiers
| Identifier | Who creates it | What it's for |
|---|---|---|
| GTIN (UPC, EAN, ISBN) | You, bought from GS1 | The global product barcode. Usually required to create a new listing. |
| ASIN | Amazon | Amazon's ID for the product page. One ASIN per product, shared by every seller offering it. |
| SKU | You | Your own internal code for your offer. Each seller has their own SKU for the same ASIN. |
| FNSKU | Amazon | The FBA barcode that identifies your units in Amazon's warehouses. Starts with "X00" for most products. |
A good SKU format makes reports much easier to read, for example BRAND-PRODUCT-SIZE-COLOR.
For GTINs, buy them directly from GS1. Amazon checks barcodes against the GS1 database, and cheap resold UPCs often cause listing errors.
Manufacturer barcodes vs Amazon barcodes
When you send stock to FBA, Amazon needs to scan each unit. There are two ways it can identify your product:
- Amazon barcode (FNSKU): a label unique to you as the seller. Amazon tracks your units separately from anyone else's.
- Manufacturer barcode (the UPC or EAN printed on the packaging): used to be allowed for any eligible product, with the inventory potentially commingled, meaning mixed with identical units from other sellers.
What changed in 2026
Amazon has ended stickerless, commingled inventory. From March 31, 2026, new FBA inventory has to be tracked to the seller who sent it:
- Resellers must label every unit with an FNSKU, even if it already has a manufacturer barcode.
- Brand owners with the Brand Representative role in Brand Registry can still use the manufacturer barcode for their own products, because only they sell that product. Products without a manufacturer barcode still need an FNSKU.
- Stickerless inventory already in FBA can sell through. You don't need to recall it.
- Amazon also stopped offering its FBA labeling and prep service for US shipments created from January 1, 2026, so labeling has to be done before stock arrives.
For brand owners, this is good news. Commingling meant your customers could receive a unit sent in by another seller, including counterfeits, and you'd get the bad review. That risk is now gone.
Check your settings under Settings > Fulfillment by Amazon > FBA product barcode preference before your next shipment.
Labeling tips
- Print FNSKU labels from the shipment workflow in Seller Central, on removable labels if possible.
- Cover any other scannable barcode on the packaging, so the warehouse scans the right one.
- Check that the label matches the product, especially for size and color variations that look alike.
- Ask your supplier to apply labels at the factory. It's cheaper and avoids prep fees.
- Don't forget carton labels: each box needs its own shipment label.
Key takeaways
- GTIN for listing, ASIN for the product page, SKU for your records, FNSKU for FBA.
- Buy GTINs from GS1.
- Resellers now need FNSKU labels on every unit. Brand owners can use manufacturer barcodes for their own products.
- Label at the factory, and double-check variations.
Shipment and labeling errors are easy to avoid with a routine. Our inventory management service plans each restock and checks shipments before they leave the factory.