Amazon Barcode Requirements: GTIN vs FNSKU, GS1 Verification, GTIN Exemption and FBA Label Sizes
Most Amazon barcode problems are not printing problems. They come from mixing up two different identifiers — the GTIN that identifies the product and the FNSKU that identifies your inventory — and from buying UPCs that do not belong to you. This guide walks through what Amazon actually checks, which barcode ends up on the unit, and how to print it so the fulfilment centre scans it first time. Amazon updates its help pages regularly; treat the numbers below as the current rules and confirm in Seller Central before a large run.
Key points
- Two unit barcodes exist: the manufacturer barcode (a GS1 GTIN — UPC-A, EAN-13, ISBN) and the Amazon barcode (FNSKU, printed as Code 128, starting with X00).
- Amazon verifies your UPC against the GS1 registry. Codes bought from resellers carry someone else's company prefix and are rejected as invalid.
- No GS1 codes? Apply for a GTIN exemption by category and brand, then label units with the FNSKU.
- FBA label: FNSKU barcode + product name + condition, black on white matte, 1×2 in to 2×3 in, about 0.25 in between barcode and label edge, flat surface, cover every other barcode.
- Print at 300 dpi on thermal or laser at 100 % scale; scan a sample before labelling the batch.
1. The two barcodes and when each is used
| Manufacturer barcode | Amazon barcode | |
|---|---|---|
| What it is | GTIN issued by GS1: UPC-A (12 digits), EAN-13, or ISBN for books | FNSKU: Amazon's inventory identifier, e.g. X001ABC2DE, 10 characters |
| Symbology | UPC-A / EAN-13 (linear, numeric) | Code 128 (linear, alphanumeric) |
| Who prints it | Usually the manufacturer on the retail packaging | You (or Amazon's labelling service) on a sticker |
| Inventory model | Eligible for commingled (stickerless) inventory: identical units from any seller are pooled | Tracked to your seller account only |
| When Amazon requires it | To create the listing in most categories | If you opt out of commingling, if the product has no GTIN (exemption), if the item is used, or if the same GTIN maps to variations Amazon needs to tell apart |
| Where the data lives | Product identity — shared across the catalogue | One ASIN in one seller's inventory |
The practical consequence: the listing is created with a GTIN, but the sticker that goes on the unit is often an FNSKU. Sellers who print the UPC from their listing onto FBA units when Amazon expects FNSKU labels will get the shipment flagged, and vice versa. Check the "Label" column in the shipment workflow — it tells you which barcode the fulfilment centre expects for each SKU.
2. Why Amazon rejects UPCs — and how to get valid ones
Every GTIN starts with a GS1 Company Prefix that GS1 licensed to one company. Amazon looks the prefix up in the GS1 registry and compares the licensee to the brand on your listing. Three situations fail:
- Resold codes. Cheap "UPCs" sold in bulk online come from prefixes licensed decades ago to other companies. The GS1 record shows that company, not you. These are the majority of "invalid product ID" errors.
- Brand mismatch. You hold a legitimate GS1 licence but the listing brand does not match the GS1 record (different legal entity, distributor listing a manufacturer's product under their own brand).
- Reused numbers. A GTIN already attached to a different product in Amazon's catalogue.
The fix is to license codes directly from GS1: a GS1 US single-GTIN licence or a company prefix subscription in North America, or the GS1 member organisation in your country for EAN-13. The barcode image itself is then trivial — enter the 12 or 13 digits in the barcode generator and it computes the check digit and draws a symbol at GS1 nominal size.
GTIN exemption. Brands that do not use GS1 codes (handmade goods, private-label bundles, parts without retail packaging, some generics) can request a GTIN exemption in Seller Central for a category and brand. Once approved, listings in that scope are created without a UPC and units are labelled with the FNSKU. The exemption is per category, not account-wide, and Amazon may ask for product images showing the branding and the absence of a barcode.
3. FBA label requirements
When the fulfilment centre expects an Amazon barcode, each sellable unit needs one label that meets these rules:
| Element | Requirement |
|---|---|
| Content | FNSKU barcode, human-readable FNSKU, product name, condition (e.g. New) |
| Symbology | Code 128 — this is what Seller Central's PDF uses and what the scanners expect |
| Size | Between 1 × 2 in (25 × 51 mm) and 2 × 3 in (51 × 76 mm). Common: 1 × 2⅝ in (Avery 5160, 30 per sheet) for laser; 2 × 1 in or 2.25 × 1.25 in on thermal rolls |
| Colour and stock | Black print on white, non-reflective (matte) label stock; no coloured or glossy labels |
| Quiet zone | About 0.25 in (6 mm) clear space between the barcode and the label edge on both sides |
| Placement | On a flat surface, not across a seam, corner or curve; not on the bottom if avoidable; readable without opening the packaging |
| Other barcodes | Cover every other scannable barcode on the unit (UPC, EAN, retailer codes) so a scanner cannot pick up the wrong one |
| Sets and bundles | One label per sellable unit; multi-piece sets also need a "Sold as set" marking so the pieces are not separated |
Two details cause most rejections at receiving. First, scaling: the Seller Central PDF is sized for a specific layout, and printing it with "fit to page" shrinks the bars until the X-dimension is no longer a whole number of printer dots. Print at 100 %. Second, uncovered UPCs: a unit carrying both a visible UPC and an FNSKU is ambiguous, and Amazon may receive it as the wrong product or commingle it unintentionally.
4. Printing FNSKU labels in bulk
- Export the FNSKU list from Seller Central (Manage Inventory → columns FNSKU, product name, condition).
- Load the list into the batch barcode generator with symbology Code 128; add the product name as the text line under each barcode. Keep the FNSKU column as text in Excel so nothing is reformatted.
- Choose the layout: the 30-up 1 × 2⅝ in sheet for a laser printer, or a 2 × 1 in roll for a thermal printer. Templates for both are in the template library.
- Print at 100 % on a 300 dpi printer. 203 dpi thermal printers work if the X-dimension is set to a whole number of dots (3 dots = 0.375 mm is safe for Code 128 at this size).
- Scan one label from each sheet or roll with a handheld scanner before applying. A phone camera is not a valid test — see why barcodes scan on a phone but not on a scanner.
5. Case and shipment labels are a different thing
Amazon does not require an ITF-14 on the case for FBA; it requires its own FBA box ID label (a Code 128 shipment identifier) on each box, plus carrier labels. If the same cases also go to brick-and-mortar retail or a 3PL, add the GS1 ITF-14 case code for those channels — Amazon ignores it. Prep labels such as the polybag suffocation warning, "Sold as set", "Ready to ship" and "Team lift" are text markings, not barcodes, and follow Amazon's packaging and prep requirements.
Transparency is a separate brand-protection programme: each unit carries a unique 2D code (Data Matrix or QR with the Transparency "T" logo) that Amazon scans to authenticate the item. Transparency codes are issued by Amazon per unit and are printed in addition to, not instead of, the FNSKU or GTIN.
Generate UPC-A, EAN-13 or FNSKU (Code 128) barcodes
Enter the digits or the FNSKU, pick the symbology, download SVG or PNG at 300 dpi. For a whole inventory list, use the batch tool with a 30-up or roll layout. Open the tool →
References
- Amazon Seller Central — Product ID (GTIN) requirements, GTIN exemption, and FBA product barcode requirements (log-in required; wording and sizes are updated periodically).
- GS1 US — UPCs, barcodes and company prefixes
- GS1 General Specifications — GTIN structure, UPC-A / EAN-13 dimensions and quiet zones
Frequently asked questions
Do I need a UPC to sell on Amazon?
Usually yes. Most categories require a GS1-issued GTIN (UPC-A in North America, EAN-13 elsewhere) to create a listing, and Amazon checks the number against the GS1 registry. If your brand does not have GS1 codes, apply for a GTIN exemption in Seller Central for the relevant category and brand; approved listings then use an FNSKU as the unit barcode instead.
What is the difference between a UPC and an FNSKU?
The UPC (or EAN) is the manufacturer barcode, a GS1 GTIN that identifies the product regardless of who sells it. The FNSKU is Amazon's own identifier for one product in one seller's inventory, printed as a Code 128 barcode starting with X00. Manufacturer-barcode units can be commingled with other sellers' stock; FNSKU-labelled units are tracked to you.
Why does Amazon say my UPC is invalid?
Amazon verifies the GS1 Company Prefix embedded in the UPC against the GS1 database. Codes bought from third-party resellers belong to someone else's prefix, so the brand on file does not match yours and the listing is rejected. Buy codes directly from GS1 (a GS1 US UPC subscription or a GS1 member organisation in your country), or apply for a GTIN exemption.
What size should an FBA label be?
Amazon accepts labels from 1 × 2 inches up to 2 × 3 inches; 1 × 2⅝ inches (the 30-per-sheet Avery 5160 layout) and 2 × 1 inches on thermal rolls are the common choices. The label must show the FNSKU barcode, the product name and the condition, printed black on white non-reflective stock, with about 0.25 inch between the barcode and the label edge, placed on a flat surface, and it must cover every other scannable barcode on the unit.
Can I print FNSKU labels myself?
Yes. Download the label PDF from Seller Central, or generate Code 128 barcodes from your FNSKU list with a batch barcode tool, then print on a 300 dpi thermal printer or a laser printer on matte labels. Avoid inkjet on glossy stock and never scale the barcode — scan a sample from each batch before you label the shipment.