By Karla Urdaneta, Operations Manager at ShipHouse. Karla's team preps and labels inventory for Amazon FBA every day in our New Jersey and Delaware warehouses.
An FNSKU label is the Amazon barcode, starting with "X00", that identifies a unit as yours inside Amazon's fulfillment network. In 2026 it matters more than ever. Amazon ended commingling on March 31, 2026, so most sellers now need an FNSKU on every unit. Amazon also stopped applying labels for sellers in the U.S. on January 1, 2026, so you, your supplier, or a prep center has to do it.
This guide covers what an FNSKU is, the exact label specs Amazon publishes, where the label goes, and how to avoid the mistakes that get units flagged at receiving.
What is an FNSKU?
FNSKU is commonly expanded as Fulfillment Network Stock Keeping Unit. Amazon calls these labels "Amazon barcodes" or "X00 labels." Amazon generates one for each product you sell through FBA, and it links a physical unit to your seller account rather than just to the product.
That's the key difference from the other codes on your listing:
Code | Who assigns it | What it identifies | Where you see it |
|---|---|---|---|
FNSKU | Amazon | Your units of a product, in Amazon's fulfillment network | The label on each unit (starts with X00) |
ASIN | Amazon | The product listing in Amazon's catalog, shared by every seller of that product | Product page and Seller Central |
UPC / EAN / GTIN | The brand, via GS1 | The product, everywhere it's sold | Printed on the manufacturer's packaging |
Seller SKU | You | Your internal inventory record | Seller Central and your own systems |
Two rules follow from this. Each variation needs its own FNSKU: every size and color is a separate product. Each condition needs its own FNSKU too, so "Used – Like New" and "Used – Good" are labeled differently.
What changed in 2026
Two announcements changed FNSKU labeling for U.S. sellers:
Date | Change | What it means for you |
|---|---|---|
July 28, 2025 | Amazon announces the end of its FBA Prep and Label Services in the U.S. | Plan who will label and prep your inventory. |
January 1, 2026 | Amazon stops prepping and labeling U.S. inventory, including inventory moving through AWD and Amazon's other inbound programs | Units that arrive without proper labels or prep aren't reimbursable if they're damaged or can't be traced. |
December 8, 2025 | Amazon announces the end of commingling | Plan your switch to FNSKU labels. |
March 31, 2026 | Commingling ends for inventory shipped on or after this date | Resellers must use FNSKU labels even when a UPC is present. |
Commingling meant Amazon could fulfill your order with another seller's identical unit, as long as both carried the same manufacturer barcode. That's over. Customers now receive only the inventory of the seller they bought from, and the same applies to returns and removals.
Amazon's labeling service used to cost $0.55 per unit, more for items that also needed bagging or bubble wrap. That service is gone, so the work has moved to sellers, suppliers, and third-party prep centers.
Do you need FNSKU labels?
Since March 31, 2026, the answer depends on who you are:
- Brand owners with the Brand Representative role in Brand Registry can skip FNSKU stickers. The product must be new, carry one scannable UPC, EAN, or ISBN that matches a single ASIN, and be registered to your brand. Enrolling the brand alone isn't enough.
- Resellers, including authorized resellers, must apply FNSKU labels, even if the product has a UPC.
- Products without a manufacturer barcode, including products with a GTIN exemption, need an FNSKU for everyone.
- Inventory that was already in Amazon's network or in transit before March 31, 2026 can keep selling under its original SKU. Only new shipments need FNSKU labels.
Switching from the manufacturer barcode to an Amazon barcode creates a new SKU in Seller Central. Your reviews and ratings stay with the ASIN, so they aren't lost.
FNSKU label requirements
These are the specs Amazon publishes for Amazon barcode labels:
Requirement | Amazon's spec |
|---|---|
Label size | Between 1 × 2 in and 2 × 3 in (for example 1 × 3 in or 2 × 2 in) |
Material | Black ink on white, non-reflective labels with removable adhesive |
White space | At least 0.25 in on the left and right and 0.125 in on the top and bottom, both around the barcode and its text and between the content and the label edges |
Required text | The FNSKU, the product name, and the item condition |
Durability | Readable and scannable for 24 months |
Printer | Thermal (recommended) or laser, 300 dpi or higher. No inkjet printers. |
Print scaling | "None" or 100%. Scaled labels may not scan. |
Amazon's own fulfillment centers print with direct thermal printers. If you print on sheets, Seller Central supports 21-, 24-, 27-, 30-, 40-, and 44-up templates. The 30-up template (1 × 2⅝ in on U.S. Letter) is the common U.S. choice.
If you print the FNSKU directly onto your packaging instead of using a sticker, the same size, contrast, and white-space rules apply.
Where to put the FNSKU label
Placement is where most labeling problems come from. Amazon's rules:
- Put it on a flat surface, never across a curve, corner, or seam.
- Keep it at least 0.25 in from the edges of the package.
- Cover every other scannable barcode, such as the UPC, so the FNSKU is the only one a scanner can read. Two exceptions: don't cover serial-number barcodes or Transparency codes.
- Don't cover warning, safety, or compliance labels.
- Make sure it scans after prep. If the unit goes into a poly bag, the label must scan through the bag, or go on the outside of it.
- Label every unit in a case pack, and remove or cover any barcodes on the case itself.
FNSKU labels vs. other FBA labels
Unit labels aren't the only labels in an FBA shipment:
Label | Goes on | Key rule |
|---|---|---|
FNSKU label | Every unit | 1 × 2 in to 2 × 3 in; only scannable barcode on the unit |
FBA box ID label | Every shipping box | Unique to each box (never photocopied); 3⅓ × 4 in, or 4 × 6 in thermal; on a flat face, off the seams |
Carrier label | Every shipping box | Next to the box ID label, not covering it |
"Sold as set" label | Sets and bundles | "Sold as set" or "This is a set. Do not separate" |
Suffocation warning | Poly bags with an opening of 5 in or more | Printed on the bag or applied as a label |
Expiration date | Dated products, on each unit and the master carton | MM-DD-YYYY or MM-YYYY, at least 36-point, outside any bag or wrap |
If you don't provide box content information, Amazon charges a manual processing fee: $0.15 per unit from January to October, and $0.30 per unit in November and December.
How to print FNSKU labels in Seller Central
You can print labels in two places:
- Send to Amazon: select Print SKU labels for one SKU, or Print all SKU labels at the end of step 1. You can also print from View contents in steps 2 to 5.
- Manage Inventory: open the product's menu and choose Print item labels.
Choose the template that matches your label stock and set print scaling to None or 100%. Print one test label and scan it before you run the whole batch.
Common FNSKU labeling mistakes
Amazon groups receiving problems into four categories: missing barcodes, mislabeled units, unscannable barcodes, and prep or labeling errors. These are the habits that cause them:
- Leaving the UPC uncovered, so the scanner reads the wrong barcode
- Using one FNSKU across sizes, colors, or conditions
- Printing on an inkjet printer, or with scaling that shrinks the barcode
- Putting the label on a curve, corner, or seam, or under a poly bag where it can't be scanned
- Leaving barcodes on case-pack cartons
- Shipping stickerless as a reseller after March 31, 2026
The cost goes beyond a re-label. Units that need an FNSKU and arrive without one are marked defective: Amazon applies a sticker and reports the defect. Since January 1, 2026, units that arrive without proper labels or prep aren't reimbursable if they're damaged or can't be traced. Amazon may also charge unplanned prep fees.
Label it yourself or use a prep center?
Labeling yourself makes sense at low volume, or when your products arrive at your own location anyway. You need a thermal printer, label stock, and the time to cover barcodes and check scans.
A prep center or 3PL makes sense when inventory arrives from a manufacturer or importer in volume, when units also need poly-bagging, bundling, or carton and pallet prep, or when you'd rather ship smaller, more frequent replenishments into FBA.
For comparison, Amazon used to charge $0.55 per unit for labeling. ShipHouse's published prep rates start at $0.40 per unit for FNSKU labeling, $1.00 per unit for poly-bagging or bubble-bagging, and $1.25 per unit for bundles of two. See our pricing and FBA prep services. Our New Jersey and Delaware warehouses receive inventory close to the New York/New Jersey port, label and prep it, and send it into FBA.
Frequently asked questions
What is an FNSKU?
An FNSKU is the Amazon barcode, starting with X00, that identifies a unit as belonging to a specific seller inside Amazon's fulfillment network. Amazon assigns one to each product you sell through FBA.
What's the difference between an FNSKU and an ASIN?
The ASIN identifies the product listing and is shared by every seller of that product. The FNSKU identifies your units of that product, so Amazon knows whose inventory it is.
Do I need FNSKU labels if my product already has a UPC?
Since March 31, 2026, yes, unless you're the brand owner with the Brand Representative role and the product is new, registered to your brand, and carries one scannable UPC, EAN, or ISBN that matches a single ASIN. Resellers, including authorized resellers, must use FNSKU labels.
What size does an FNSKU label have to be?
Between 1 × 2 in and 2 × 3 in. The 30-up template (1 × 2⅝ in) is the most common choice for U.S. Letter sheets.
Can I print FNSKU labels on an inkjet printer?
No. Amazon recommends thermal printers, accepts laser printers, and says not to use inkjet printers. Print at 300 dpi or higher, with scaling set to none or 100%.
Where should the FNSKU label go?
On a flat surface, at least 0.25 in from the edges, covering any other scannable barcode such as the UPC. Don't cover serial-number barcodes, Transparency codes, or safety and compliance labels.
Does Amazon still apply FNSKU labels for a fee?
Not in the U.S. Amazon's FBA Label Service, previously $0.55 per unit, ended on January 1, 2026. Sellers now label inventory themselves or use a prep center.
What happens if my units arrive without FNSKU labels?
Units that need an FNSKU and arrive without one are marked defective. Amazon applies a label and reports the defect, and the units aren't reimbursable if they're later damaged or can't be traced.
Will switching to FNSKU labels reset my reviews?
No. Switching creates a new SKU, but reviews and ratings stay with the ASIN.
Does each size, color, or condition need its own FNSKU?
Yes. Every variation and every condition has its own FNSKU, so each needs its own label.
Do GTIN-exempt products need FNSKU labels?
Yes. Products with a GTIN exemption have no manufacturer barcode for Amazon to track, so they must carry FNSKU labels.
The bottom line
FNSKU labeling is a small task that decides whether your inventory gets received, sold, and reimbursed. Since 2026, most sellers need it on every unit, and Amazon no longer does it for you. Get the specs and placement right once, write them into your supplier or prep instructions, and check a scan before every shipment.
If you want inventory received, labeled, and prepped before it goes into FBA, tell us about your products and volume.
Requirements in this guide come from Amazon Seller Central help pages and announcements, current as of November 2026. Amazon updates its requirements regularly, so check Seller Central before you change your process. The featured image is AI-assisted and was created from photos of the ShipHouse team.
