The short answer
Most brands and resellers should use FNSKU labels rather than the manufacturer barcode. An FNSKU, or Fulfillment Network Stock Keeping Unit, is a barcode Amazon assigns to your specific offer. It ties every unit to your seller account. The manufacturer barcode, usually a UPC or EAN, identifies the product but not the seller, so units sent on that barcode can be commingled with identical units from other sellers.
The manufacturer barcode can save labeling cost, and for some brands with tight control of their distribution it works well. But for most sellers, the protection an FNSKU gives is worth the cost of a label.
How commingling works
When units are received on the manufacturer barcode and the listing is eligible, Amazon may treat them as interchangeable with identical units from other sellers using the same barcode. When a customer orders from you, Amazon can ship the nearest matching unit, which may have been sent in by another seller.
That speeds delivery and spares you the labeling step, but it removes your control over what your customer actually receives. If another seller sends counterfeit, damaged or expired units under the same barcode, your customer may get one, and the complaint lands on your account. You may also find it hard to prove which units were yours in an authenticity dispute.
When FNSKU labels make sense
FNSKU labels are the safer choice in most situations:
- Wholesale and arbitrage sellers who sell the same products as many other sellers
- Any product category where counterfeits are common
- Products with expiration dates, where another seller's short-dated stock could reach your customer
- Products where condition and authenticity complaints carry serious account risk
- Brands that want clean, traceable inventory records
The cost is labor and material for one label per unit. Many factories can apply FNSKU labels during packing, which lowers that cost, though factory labels should be audited when inventory arrives.
When the manufacturer barcode can work
Using the manufacturer barcode can work for brands that are the only seller of their products, have full control of distribution and are enrolled in programs that limit commingling of their brand. In that case, the risk of another seller's units being mixed with yours is low, and skipping labels saves time.
It also matters that the barcode is valid and registered to your product. Amazon generally expects product barcodes to be legitimate GS1 identifiers. If your barcode is shared with other products or is not registered properly, units can be received under the wrong listing. Check eligibility for barcode-based tracking for each listing in Seller Central before deciding.
Label placement and the exposed barcode problem
Whichever barcode you use, Amazon's receiving scan must find exactly one scannable code. If you use FNSKU labels, every manufacturer barcode on the unit must be covered. A partially exposed UPC next to an FNSKU is one of the most common prep mistakes, and it can cause units to be received under the wrong identifier.
Good practice:
- Place the FNSKU label directly over the manufacturer barcode when possible
- Cover any secondary barcodes on other faces of the packaging
- Keep labels flat and away from seams and corners
- Use removable labels if the product may later sell in a different channel
- Scan-verify each labeled unit before packing
Switching from manufacturer barcode to FNSKU
Switching a listing from manufacturer barcode to FNSKU is done in Seller Central by changing the barcode type for the offer. New shipments then need FNSKU labels on every unit. Inventory already in Amazon's network stays as it was received.
Plan the switch so the change applies to your next inbound, update your work instructions for the SKU and tell your factory or prep center before the next production run. If units have already been labeled with the manufacturer barcode for a pending shipment, they will need FNSKU labels applied before they ship once the change takes effect.
Label quality and printing tips
An FNSKU label only protects you if Amazon can read it. Poor print quality is a surprisingly common cause of receiving problems, and it is easy to prevent.
Practical guidelines for FNSKU labels:
- Use a thermal or laser printer that produces sharp, high-contrast bars; worn thermal print heads cause faint or broken lines
- Use label stock that sticks firmly to your packaging surface and does not peel in cold or humid conditions
- Print the label at a size Amazon supports, without stretching or shrinking the barcode
- Keep the label flat; labels wrapped around a curved bottle or across a box edge may not scan
- Avoid placing labels over shrink-wrap seams, where they can wrinkle
- Check that the human-readable text includes the FNSKU, product name and condition
Scan a sample of every batch before applying it. A label that looks fine can still fail to scan if the print density is wrong.
For products where you may later sell through another channel, consider removable label stock so FNSKU labels can be taken off cleanly. This is especially useful if you hold reserve inventory that might be allocated to Walmart WFS, TikTok Shop or wholesale customers. If a factory prints your labels, send it the exact label file from Seller Central rather than letting it recreate the barcode, and audit a sample of every SKU when the shipment arrives at your prep center. A single mismatched label file can affect an entire production run, so this check is worth doing every time.
Bundles, multipacks and other channels
Bundles and multipacks always need their own barcode because they are a different product from the individual unit. For Amazon, that is usually an FNSKU for the bundle listing, with every component barcode covered and a sold-as-set label on the package.
Other marketplaces work differently. Walmart WFS relies on the GTIN set up for the item in Seller Center rather than a seller-specific label like FNSKU, so multipacks need a distinct GTIN. If you sell the same inventory on Amazon and Walmart, keep it unlabeled in reserve and apply channel-specific labeling at release, so you are not peeling FNSKU labels off units bound for Walmart.
Frequently asked questions
What is an FNSKU?
An FNSKU, or Fulfillment Network Stock Keeping Unit, is a barcode Amazon assigns to a seller's specific offer. It ties each unit to that seller's account so the units are not commingled with other sellers' inventory.
Is an FNSKU the same as a UPC?
No. A UPC identifies a product regardless of who sells it, while an FNSKU identifies your offer on Amazon. You typically need a UPC or exemption to create the listing and an FNSKU label on each unit to keep inventory tied to your account.
Can I put the FNSKU label over the UPC?
Yes, and that is usually the best placement. Every manufacturer barcode on the unit should be covered so the receiving scan reads only the FNSKU.