GLOSSARY · UPDATED OCT 20, 2026
What is an FNSKU, and what are the FNSKU label requirements?
An FNSKU (fulfillment network stock keeping unit) is the barcode Amazon uses to tie a unit in its fulfillment centers to the seller who sent it. Since Amazon ended commingling for shipments sent on or after Mar 31, 2026, the FNSKU label requirements are simple to state: resellers must label every unit, and brand owners with valid manufacturer barcodes do not have to.
Who must meet the FNSKU label requirements since Mar 31, 2026
Amazon announced the change in Seller Forums about four months ahead, and PPC Land summarized it on Mar 24, 2026. For inventory shipped to fulfillment centers on or after Mar 31, 2026:
| Seller | FNSKU on every unit? |
|---|---|
| Reseller, including an authorized reseller, without the Brand Representative role in Brand Registry | Yes |
| Brand Representative whose products carry valid manufacturer barcodes (GTIN, UPC) | No |
| Brand Representative with a GTIN exemption | Yes |
| Any seller whose product has no manufacturer barcode | Yes |
Inventory already in fulfillment centers before Mar 31 stayed under the old system. Units that arrive without a required barcode are flagged as defective, and defective units are not eligible for reimbursement (PPC Land, Mar 24, 2026).
FNSKU label specs
- Print the label from Seller Central and keep its format exactly: barcode, FNSKU or ASIN, product name and condition.
- Leave at least 0.25 inch of white space on the left and right of the barcode and 0.125 inch on the top and bottom (PPC Land, Mar 24, 2026).
- Cover any other scannable barcode on the unit, so the fulfillment center scans the right one.
- Put the label on the outside of the sellable unit, flat and readable, not across a seam or curve.
Amazon stopped offering prep and item labeling in the US from Jan 1, 2026 (Amazon developer changelog, Jul 28, 2025), so labels are applied by you, your supplier or a prep center.
Worked example: what labeling adds
Illustrative · sample figures. A reseller sends 2,000 units a month to FBA.
| Line | Amount |
|---|---|
| Prep center labeling at $0.20 a unit | $400 a month |
| Extra receiving time at the prep center | 2 days added to lead time |
| One carton of 48 units arriving unlabeled, classed defective | 48 units with no reimbursement if lost or damaged |
The fee is small. The two days matter more: add them to lead time in the reorder point calculator, and add the labeling cost to landed cost.
How labeling works on Walmart and Shopify
Walmart.
WFS does not use FNSKUs. Each unit needs a scannable GTIN (14-digit) or UPC (12-digit) barcode, each variant needs its own and FNSKU, EAN and vendor SKU codes are not accepted (Walmart, updated Aug 7, 2026). If Walmart has to label units for you, it charges $0.45 a unit when planned and $0.65 when unplanned (Walmart WFS prep services, updated Oct 8, 2026). A unit labeled for FBA is not ready for WFS: the FNSKU sticker can cover the UPC that WFS scans.
Shopify.
Shopify has no FNSKU. Your 3PL scans its own SKU barcode or the product UPC. If you ship Shopify orders from FBA stock through Multi-Channel Fulfillment, those units carry whatever Amazon required when they were received.
Shared stock.
If one pool of stock serves FBA and WFS, keep the manufacturer barcode clean and decide per shipment which label goes on. Never send FBA-labeled cartons to WFS without checking.
Common mistakes
-
Assuming brand owners never label.
A GTIN exemption or a product without a manufacturer barcode still needs FNSKU labels.
-
Leaving two barcodes visible.
The scanner may read the wrong one.
-
Trimming the margins.
Labels that break the white-space rule can fail to scan at receiving.
-
Forgetting lead time.
Labeling adds days at the prep center or the supplier.
-
Reusing FBA cartons for WFS.
WFS needs the UPC or GTIN visible on every unit.
What is the difference between an FNSKU and a UPC?
A UPC is a 12-digit manufacturer barcode that identifies the product anywhere. An FNSKU is Amazon's own code that identifies the product and the seller inside Amazon's fulfillment network. Since Mar 31, 2026, brand owners with valid UPCs can often rely on the UPC; resellers need the FNSKU.
Do I need FNSKU labels if I own the brand?
Usually not, if you hold the Brand Representative role in Brand Registry and your products carry valid manufacturer barcodes. You still need them if you have a GTIN exemption or the product has no barcode. Check your listing's barcode setting in Seller Central before each shipment.
What happens if units arrive without labels?
Units without a required barcode are flagged as defective at receiving and are not eligible for reimbursement if they are later lost or damaged. Fixing labels after the fact costs more than labeling before the shipment leaves.
Can Amazon still label my units for me?
Not in the US. Amazon's prep and item labeling services ended on Jan 1, 2026. Use a prep center, your supplier or your own team, and confirm they print from Seller Central.
Can I use the same labels for Walmart WFS?
No. WFS needs a scannable GTIN or UPC on each unit and does not accept FNSKUs. Keep the manufacturer barcode visible on units bound for WFS.
Can you manage inbound labeling for us?
Yes. Our Amazon inventory and fees service manages inbound shipments and labeling checks, and WFS management does the same for Walmart. See pricing.
Sources4 sourcesLast checked Oct 20, 2026
- 01ppc.landcommingling ends for shipments on or after Mar 31, 2026; who must label; label margins; unlabeled units defective and not reimbursable; cites Amazon's Seller Forums announcement; Mar 24, 2026; press; checked Oct 20, 2026Primary
- 02developer-docs.amazonAmazon prep and item labeling end in the US from Jan 1, 2026; Jul 28, 2025; checked Oct 20, 2026Primary
- 03marketplacelearn.walmart.comeach WFS unit needs a scannable GTIN or UPC; FNSKU not accepted; updated Aug 7, 2026; checked Oct 20, 2026Primary
- 04marketplacelearn.walmart.comitem labeling $0.45 a unit planned, $0.65 unplanned; updated Oct 8, 2026; checked Oct 20, 2026Primary
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