UPC, GTIN-14 or FNSKU: which barcode Amazon reads, and the packaging mistakes that block your stock

Your cartons reach Amazon's warehouse, and days later the units still aren't available to sell. Or your shipment plan drops one product before it even leaves your dock. Often the cause is a barcode that looks perfectly fine to you and your designer. Amazon reads one specific number on each unit. If that number doesn't match its catalogue, your stock waits. In the middle of Q4, waiting can cost you weeks of selling.

Three numbers, three jobs

Every product on Amazon has an ASIN, Amazon's ID for the product page. The physical unit needs a barcode Amazon can scan and connect to that ASIN. Three numbers tend to get mixed up.

• UPC-A (12 digits) or EAN-13 (13 digits). This is your manufacturer barcode, the one printed on the retail unit. Amazon's labelling guide lists UPC, EAN, JAN, ISBN and GCID as the manufacturer barcodes it works with.
• GTIN-14 (14 digits). This is a case code. Under the GS1 barcode standards, it identifies a carton or inner pack of units and is usually printed as an ITF-14 barcode on corrugated boxes. It is built for warehouses and wholesale shipments. The checkout scanner never sees it.
• FNSKU. Amazon's own barcode, created in Seller Central for one seller's offer on one ASIN. It links each unit to the seller who sent it.

Amazon says every item you send needs a scannable barcode. Which of these it reads on the unit depends on who is sending the stock.

When Amazon accepts your own barcode

Amazon changed the rules on March 31, 2026, when it ended commingling. Commingling meant Amazon could ship a customer the identical unit stored closest to them, even if another seller had sent it in. With that gone, the barcode rules for FBA (Fulfillment by Amazon, where Amazon stores and ships your orders) depend on who is selling.

• Brand owners who hold the Brand Representative role in Brand Registry, Amazon's program for verified brand owners, can ship on the manufacturer barcode already printed on the product. No Amazon sticker needed.
• Resellers, meaning any seller without that role, must put an Amazon barcode sticker on the product, even when it carries a UPC.
• Products with no manufacturer barcode need Amazon stickers, whoever sends them.

Amazon announced the same rule on Amazon.ca and Amazon.com. One difference matters for US shipments. Since January 1, 2026, Amazon no longer offers prep or item labelling for FBA shipments to the US store, so if a sticker is needed, you or your 3PL apply it before the cartons leave. Amazon also said units sent without the right prep and labels won't be reimbursed if they are damaged or can't be traced.

Two packaging mistakes that match nothing

In our experience, the barcode that blocks stock is rarely missing. It is printed, it scans, and it points to nothing in Amazon's catalogue. Two mistakes cause most of it.

The leading zero disappears. Many North American UPCs start with 0. Spreadsheets drop it. So do some label tools and systems that tidy numbers by stripping zeros from the front. Your 12-digit UPC becomes 11 digits. When we have looked up truncated codes like this, they matched no product, while the full 12-digit code found the right ASIN straight away. The same thing happens when a tool shortens a 14-digit code by removing every leading zero instead of exactly two.

The case code goes on the unit. Your GS1 account or ERP may store a 14-digit GTIN for each item, and a designer may print that number on the retail box. A UPC-A barcode can only hold 12 digits, so a 14-digit number ends up in a different barcode format that retail scanners aren't set up to read. Put the 12-digit UPC-A on the unit. Keep the GTIN-14 for cartons.

One small thing that is fine: some scanning apps show a UPC-A as a 13-digit number with an extra 0 in front. That is normal. Don't change the artwork to match it.

When a seller can't ship on your UPC

If someone other than your Brand Representative sends your product to FBA, such as a distributor or a retail partner, the manufacturer barcode is off the table for them. In our experience, the sign shows up in the shipment plan: Amazon removes the product and says the seller isn't eligible to use the manufacturer barcode because they aren't the brand representative. It tends to hit older offers that were set up to track by manufacturer barcode.

The fix we use is usually quick. The seller creates a new SKU, their own reference for an offer, on the same ASIN. Amazon assigns that new offer a real FNSKU, often within minutes. The seller prints FNSKU labels, applies them to each unit and ships that SKU on a separate shipment. Your packaging can stay exactly as it is.

One more trap. When a seller opens their own listing and sees an empty barcode field, it only means they never entered a UPC on their offer. Amazon's catalogue record for the ASIN can still hold your UPC or EAN. In our experience, checking the catalogue record before concluding that Amazon has no barcode saves a needless relisting or reprint.

Amazon matches a box to a listing through one number on the unit. Get that number right on the artwork, keep it intact in your files, and know who is allowed to ship on it. Most barcode blocks we see are fixed with a new SKU and a sheet of labels, as long as someone spots them before the Q4 cartons are sealed.