The FNSKU is the Amazon barcode that assigns every unit in Amazon's warehouses to a seller. Since 31 March 2026 it has been mandatory for resellers: Amazon has ended commingled inventory. If you sell branded products through online arbitrage or wholesale, you must label every product with an FNSKU label. In this guide you will learn what the FNSKU is, how it differs from EAN, GTIN and ASIN, who needs it, its benefits and how to print and apply FNSKU labels correctly.
What is an FNSKU?
FNSKU stands for Fulfilment Network Stock Keeping Unit. Amazon creates this number for every product in your seller account that you sell through Fulfilment by Amazon (FBA). The FNSKU is unique to you as a seller: if five sellers offer the same product, each has their own FNSKU.
- Format: ten characters of letters and digits. Amazon's own barcodes usually start with X00.
- Purpose: at check-in and in storage, fulfilment centre staff scan the FNSKU barcode and immediately know which seller owns the unit.
- Where to find it: in Seller Central under "Manage Inventory" next to each SKU.
FNSKU, ASIN, EAN, GTIN and SKU: the differences
| Code | Issued by | Used for |
|---|---|---|
| ASIN | Amazon | identifies the product in the catalogue, the same for all sellers |
| EAN / GTIN | GS1 (manufacturer) | globally valid manufacturer barcode, 13 digits |
| UPC | GS1 (manufacturer) | barcode mainly for North America, 12 digits |
| ISBN | ISBN agency | number for books, equal to the ASIN for books |
| FNSKU | Amazon | assigns every unit to your account in FBA storage |
| SKU | you | your internal item number |
Is the ASIN the same as the EAN? No. The EAN is the manufacturer's number and works on every platform, online or in store. The ASIN is Amazon's catalogue number, usually linked to an EAN. More in our guide What is an ASIN?
Is an EAN the same as a GTIN? Almost. GTIN is the umbrella term, and the EAN (now GTIN-13) is the standard format in the UK and Europe.
The end of commingling: FNSKU mandatory for Amazon FBA since 31 March 2026
Sellers used to be able to use the manufacturer barcode with FBA. Stock from different sellers was then stored together (commingled inventory), and Amazon simply shipped the nearest unit. That was fast but caused problems with counterfeits: if one seller sent in fake stock, another could receive the complaints. Since 31 March 2026 Amazon has ended commingling. Every unit is clearly assigned to one seller.
- Resellers (online arbitrage, retail arbitrage, wholesale): you must label every unit with an FNSKU label, even if the product has an EAN. Without a correct label, Amazon will not check the stock in as FBA inventory.
- Brand owners with Amazon Brand Registry: you may keep using the manufacturer barcode. Amazon then assigns your units to your account virtually.
For arbitrage sellers this means more work per unit. Build the time or cost of labelling into every calculation. Our guide to Amazon FBA costs shows how it affects your total costs.
Benefits of the FNSKU for Amazon FBA sellers
- Protection from other sellers' stock: customers only receive your own units, so counterfeits from others no longer end up under your name.
- Clean customer feedback: complaints and A-to-z claims only relate to stock you sent in yourself.
- Clear returns tracking: returned items can be assigned to your account without doubt.
How to print FNSKU labels: step by step
- Create a shipment: in Seller Central, create a shipment to Amazon or select the items under "Manage Inventory".
- Print item labels: enter the quantity and choose the format that matches your label sheet. Amazon supports sheets with 21 to 44 labels per A4 page. You get a PDF file.
- Print: ideally with a laser or thermal printer so the barcode is sharp and scannable.
- Apply: stick the label on a flat side of the packaging and fully cover old barcodes such as EAN or UPC.
- Check: spot-check with a scanner or barcode app that the code is readable.
Tip: every variation such as size or colour has its own FNSKU. Do not mix up the labels.
FNSKU label requirements
- The label shows the barcode, FNSKU, a shortened product name and the condition, for example "New".
- Use white, removable labels that come off without residue.
- Do not wrap labels over edges or curves and do not cover them with tape.
- Keep print quality high, as smudged or tiny barcodes cause check-in problems.
Labelling for Amazon FBA: label service or prep centre?
- FBA Label Service: Amazon applies the labels for a fee per unit. Convenient, but expensive for large volumes.
- Prep centre: a service provider checks, labels and packs your stock and sends it to Amazon. For arbitrage sellers with many different items, often the most efficient option. More in our prep centre guide.
EANs for Amazon: when do you need one?
To create a new product on Amazon you usually need a GTIN, in other words an EAN. Amazon checks the numbers against the GS1 database, so buy barcodes directly from GS1 UK and not from cheap resellers, or Amazon may reject the listing. As a reseller you do not need your own EAN, because you join an existing listing. If you own a brand without barcodes, you can apply for a GTIN exemption. More on sourcing your own products in Alibaba vs AliExpress.
Common Amazon barcode mistakes
- Old barcode not covered: the scanner reads the EAN instead of the FNSKU.
- Wrong labels on variations: size or colour mixed up.
- Poor print quality: inkjet prints smudge and the barcode cannot be read.
- EANs from third parties: codes not registered with GS1, so the listing gets rejected.
- Label costs not calculated: since March 2026 labelling is a fixed cost for resellers.
Before every purchase, ProfitGo shows you fees, profit and whether you can sell the product, so you can factor in the cost of labels or a prep centre straight away.
Frequently asked questions about the FNSKU
What is an FNSKU on Amazon?
The Fulfilment Network Stock Keeping Unit is Amazon's barcode that assigns every unit in FBA storage to your seller account. It usually starts with X00.
Is the FNSKU mandatory?
Since 31 March 2026, yes for resellers, because Amazon has ended commingled inventory. Brand owners with Brand Registry may keep using the manufacturer barcode.
What is the difference between FNSKU and ASIN?
The ASIN identifies the product in the catalogue and is the same for all sellers. The FNSKU identifies your units in storage and is unique to you.
Where do I find the EAN on Amazon?
On the packaging under the barcode, in Seller Central in the listing's product details, or with tools such as ProfitGo and Keepa.
Can I print barcode labels myself?
Yes. Seller Central creates a PDF with your FNSKU labels that you print on label sheets with 21 to 44 labels per page or on a thermal printer.
Does the FNSKU cost anything?
The FNSKU itself is free. Costs come from labels, printers and time, or from Amazon's label service or a prep centre.
Conclusion
Since March 2026 the FNSKU is essential for every reseller using Amazon FBA. It assigns every unit to your account and protects you from problems with other sellers' stock. Print labels cleanly, cover old barcodes and budget for labelling, and your shipments will check in without delays. Brand owners with Brand Registry can keep using the manufacturer barcode.
