FNSKU (Fulfillment Network SKU) is a unique barcode Amazon generates for each seller-ASIN combination. When a product carries an FNSKU label, Amazon can trace that unit back to the specific seller, not just the product listing.
Format example: X001ABC123 — always starts with X0 for FBA items.
FNSKU vs. ASIN vs. UPC
| Code | Purpose | Who Creates It |
|---|---|---|
| FNSKU | Seller-specific FC tracking | Amazon (auto-generated) |
| ASIN | Product identifier in Amazon's catalog | Amazon |
| UPC/EAN | Universal product barcode | GS1 / brand |
| SKU | Seller's internal reference | Seller |
Why FNSKU Matters for FBA Sellers
Amazon allows two inventory storage options for FBA:
Commingled inventory (stickered with ASIN/UPC): Your units are pooled with identical units from other sellers. A counterfeit or defective unit from another seller can end up shipped against your listing. If you receive a negative review or A-to-Z claim on that unit, it counts against you.
FNSKU-labeled inventory: Each unit is traceable to you. A defective unit from another seller cannot ship as yours. Most professional sellers use FNSKU labels for this reason.
Applying FNSKU Labels
- Go to Manage Inventory → select the ASIN
- Choose "Apply Amazon barcode" or print FNSKU from the product detail page in Seller Central
- Labels must cover the original UPC/EAN completely
- Amazon also offers a label service ($0.55/unit) if you prefer them to apply stickers at the FC
Lost or Damaged Units
Because FNSKU ties inventory to the seller, Amazon's FBA reimbursement process can accurately identify which units were lost or damaged in the FC, making claims easier to process.