A UPC is the manufacturer’s barcode: it identifies the product everywhere. An FNSKU is Amazon’s barcode: it identifies your units of that product in Amazon’s warehouses. Wholesale sellers use the UPC to find the listing, and the FNSKU to label the units they send to FBA.
Quick answer: The UPC says what the product is. The FNSKU says whose unit it is. Since Amazon ended stickerless commingling in US fulfillment centers in 2026, resellers need an FNSKU label on every unit, covering the UPC.
FNSKU vs UPC at a Glance
| UPC | FNSKU | |
|---|---|---|
| Who creates it | The manufacturer or brand (through GS1) | Amazon |
| What it identifies | The product | Your units of that product on Amazon |
| Where it is used | Any store or marketplace | Amazon fulfillment centers |
| Starts with | Usually 12 digits | Usually “X00” |
| Who prints it | Printed on the packaging | You, your supplier or a prep center |
What Is an FNSKU?
FNSKU stands for Fulfillment Network Stock Keeping Unit. Amazon assigns one to each of your FBA listings. When a worker scans it, Amazon knows the unit belongs to you, so your sales, stock and any customer problems are tied to your account.
You find it in Seller Central under your inventory, and you print it from there or from Send to Amazon.
Manufacturer Barcode vs Amazon Barcode
Until 2026, many sellers sent units with only the manufacturer barcode. Amazon then mixed (“commingled”) those units with identical units from other sellers. That saved labeling time, but it meant you could receive a complaint for another seller’s unit.
Amazon ended stickerless commingling in US fulfillment centers from March 31, 2026 (Beancount). Brand owners can generally still use the manufacturer barcode; resellers label every unit with an FNSKU.
Do I Need FNSKU Labels for Wholesale?
Yes. As a wholesale reseller you need an FNSKU label on every unit you send to FBA. The label must:
- cover the original UPC or other barcode completely
- be scannable and not wrap around a corner
- match the exact product and condition
See how to print FNSKU labels. For sets, each multipack gets its own FNSKU; see how to prep multipacks.
Common Mistakes
- Leaving the UPC visible next to the FNSKU, so the wrong code gets scanned
- Putting one product’s label on another similar product or size
- Labeling the box but not the units inside
For the full checklist, read the Amazon FBA prep requirements.
Frequently Asked Questions
Can I use the UPC instead of an FNSKU?
Only if you are the brand owner and eligible to use the manufacturer barcode. Resellers need FNSKU labels.
Is the FNSKU the same as the ASIN?
No. The ASIN identifies the product listing. The FNSKU identifies your inventory on that listing.
Can my supplier apply FNSKU labels?
Yes, if it offers labeling. We apply FNSKU labels before we ship to your FBA shipment.