If you are new to Amazon FBA, FNSKU labels might seem like unnecessary complexity. But understanding what they are and why they matter will save you from inventory problems, commingling risks, and potential account issues.
What Is an FNSKU?
FNSKU stands for Fulfilment Network Stock Keeping Unit. It is a unique barcode that Amazon generates for each product in your inventory, linked specifically to your seller account. When your product arrives at an Amazon fulfilment centre, the FNSKU tells Amazon exactly which seller this unit belongs to.
Think of it this way: a UPC or EAN barcode identifies the product (this is a 500ml blue water bottle). An FNSKU identifies your specific unit of that product (this is a 500ml blue water bottle belonging to Seller X).
FNSKU vs Manufacturer Barcode
Amazon gives you two options for how your products are tracked in their warehouses. You can use your product's FNSKU label, or you can opt into "commingled inventory" using the manufacturer's original barcode (UPC/EAN).
With FNSKU labelling, Amazon stores your units separately and tracks them back to you. When a customer orders, they ship specifically your unit. With commingled inventory, Amazon pools identical products from multiple sellers together and ships whichever unit is nearest to the customer.
Why FNSKU Is Recommended
Commingling sounds efficient, but it carries a significant risk. If another seller sends in counterfeit or damaged products of the same ASIN, Amazon might ship that defective unit to your customer under your name. You get the negative feedback and potentially the account health issue for a product that was never yours.
This is why most experienced sellers — and virtually all prep centres — recommend using FNSKU labels. It keeps your inventory separate and ensures that the units you prepped are the ones your customers receive.
How to Generate FNSKU Labels
In Seller Central, go to Manage Inventory, select the products you want labels for, and choose "Print Item Labels" from the Actions menu. Amazon generates PDF labels that you can print on standard address labels (30 per sheet, Avery compatible) or specialised barcode label stock.
The label includes the FNSKU barcode, product title (truncated), and condition. It must be printed clearly — a smudged or incomplete barcode will cause receiving issues at the fulfilment centre.
Placement Rules
The FNSKU label must be placed on a flat surface where it can be easily scanned — not wrapped around a corner or placed on a curved surface. It must not cover safety information, product instructions, or required regulatory labels on the product.
If the product has an existing scannable barcode (UPC/EAN), you should cover it with an opaque sticker or place the FNSKU label over it. Having two scannable barcodes on one unit causes confusion at the fulfilment centre and can result in the product being listed incorrectly.
Label Quality Matters
Labels must be printed at a resolution that allows clean scanning. Inkjet printers can work but thermal label printers produce consistently better results and are worth the investment if you are doing any volume. A roll of thermal labels and a basic thermal printer (like a Dymo or Zebra) pays for itself quickly in time saved and fewer receiving issues.
What Happens Without Proper Labels
Products arriving at Amazon without scannable FNSKU labels (when FNSKU labelling is required) will either be relabelled by Amazon for a fee (typically £0.15–£0.30 per unit), quarantined until you arrange relabelling, or in some cases returned or disposed of. These fees and delays are entirely avoidable with proper prep.
At Precision, FNSKU labelling is a core part of our prep service. Every unit gets a clean, accurately placed FNSKU label before it leaves our facility. It is one of those small details that prevents big problems down the line.