If you’ve been selling on Amazon for even a short time, you’ve probably run into the term FNSKU barcode. For new sellers, this acronym can be confusing, especially since Amazon already requires other identifiers like UPCs, EANs, GTINs, and ASINs.

So what exactly is an FNSKU, and why is it so important for Amazon FBA sellers?

Simply put, the FNSKU (Fulfillment Network Stock Keeping Unit) is Amazon’s internal barcode. It links your specific product to your specific seller account, ensuring that when a customer orders your item, Amazon ships the right product from the right seller.

In this complete 2025 guide, we’ll cover everything you need to know about FNSKU barcodes, including:

• What an Amazon FNSKU is (and how it differs from UPCs, ASINs, and SKUs).

• Why FNSKUs are critical for FBA sellers.

• The different types of barcodes Amazon accepts.

• Step-by-step instructions to generate and apply an FNSKU.

• Best practices to avoid mistakes and protect your inventory.

By the end, you’ll have a clear strategy for creating, labeling, and managing FNSKUs in your Amazon FBA business.

What is an FNSKU Barcode?

The FNSKU (Fulfillment Network Stock Keeping Unit) is a unique identifier Amazon assigns to each product listed through the Fulfillment by Amazon (FBA) program.

Unlike a UPC (Universal Product Code) or EAN (European Article Number), which identify the product globally, the FNSKU ties that product specifically to you  the seller.

Example:

• Brand A sells a phone case with a UPC of 123456789012.

• Multiple sellers could list under that UPC/ASIN.

• But your FBA inventory needs to be tracked separately from theirs.

• Amazon generates a unique FNSKU barcode, such as X00123ABCD, which links your inventory to your seller account.

Whenever Amazon ships an order for that ASIN from your inventory, the FNSKU ensures that your stock is decremented — not another seller’s.

👉 In short:

• UPC/EAN = product identity (global).

• ASIN = Amazon catalog identity.

• FNSKU = product identity + your seller account.

FNSKU vs UPC vs ASIN vs SKU

👉 The FNSKU is non-negotiable for every FBA product.

Why FNSKUs Matter for FBA Sellers

You might wonder: “Why can’t I just use a UPC or EAN?”

The reason is simple: Amazon needs to know which inventory belongs to which seller.

Imagine this:

• Five sellers all sell the same yoga mat under one ASIN.

• They all ship inventory to the same Amazon fulfillment center.

• Without FNSKUs, Amazon might mix up sellers’ inventory, making it impossible to guarantee the right seller gets credit for the sale.

By requiring FNSKU labels, Amazon ensures:

• Seller tracking → Your inventory is never confused with another seller’s.

• Accountability → If a buyer complains about quality, the complaint is tied to your stock only.

• Returns handling → Returned items are restocked to your account, not someone else’s.

Types of Barcodes Amazon Accepts

When creating listings for FBA, Amazon gives you two labeling options:

1. Manufacturer Barcode (UPC/EAN/ISBN):

   • Amazon pools inventory from all sellers who use the same product barcode.

   • This is called stickerless, commingled inventory.

   • Risk: If another seller ships counterfeit or low-quality stock, it could be shipped to your customers.

2. Amazon Barcode (FNSKU):

   • Inventory is separated by seller.

   • Every unit must have your unique FNSKU label.

   • This is the recommended method for private-label sellers.

👉 For long-term private-label success, always choose FNSKU labeling. It gives you control over inventory quality and accountability.

How to Generate an Amazon FNSKU Barcode (Step-by-Step 2025)

Here’s exactly how to create and download FNSKU barcodes for your products:

Step 1: Create a Product Listing

• Log in to Seller Central.

• Go to Catalog → Add a Product.

• If your product is new, select “I’m adding a product not sold on Amazon.”

• Complete the listing with title, description, images, and keywords.

Step 2: Select Fulfillment Method (FBA)

• Under Offer, choose Fulfilled by Amazon (FBA).

• This ensures Amazon generates an FNSKU for your listing.

Step 3: Find the FNSKU in Seller Central

Once your listing is created:

• Go to Manage Inventory.

• Find your product.

• In the dropdown next to Edit, select Print Item Labels.

• Amazon will display the FNSKU code.

Step 4: Print or Download the FNSKU

• Amazon provides FNSKU barcodes in a printable PDF.

• Print on label sheets (e.g., Avery 5160) or send the file to your manufacturer to print directly on packaging.

Step 5: Apply to Every Unit

• Every unit sent to an Amazon FBA warehouse must have the FNSKU.

• You can:

  • Label units yourself.

  • Pay Amazon $0.30 per unit for labeling.

  • Have your supplier print FNSKUs on product packaging at the factory.

How to Apply FNSKU Labels Correctly

• Place labels on a flat, scannable surface of the packaging.

• Cover any manufacturer UPC/EAN barcodes to prevent mis-scans.

• Ensure labels are not smudged or damaged.

• Don’t place labels on curves or seams where scanners may struggle.

👉 Pro tip: Ask your supplier to integrate FNSKU printing into packaging design — this saves time and money long term.

Common Mistakes to Avoid with FNSKUs

1. Mixing FNSKU and UPC barcodes.

   • If both are visible, warehouse workers may scan the wrong one. Always cover the UPC.

2. Wrong brand or category.

   • If your GTIN exemption doesn’t match the brand/category, Amazon won’t recognize the FNSKU.

3. Not labeling bundles.

   • Bundled sets need a unique FNSKU and must be labeled “Sold as Set.”

4. Relying on manufacturer barcodes for private-label.

   • Increases risk of inventory commingling with counterfeit sellers.

FNSKU & GTIN Exemption: How They Work Together

Many sellers confuse GTIN exemption and FNSKU requirements.

• GTIN exemption → lets you create a listing without a UPC/EAN.

• FNSKU → still required for all FBA products, even those with GTIN exemptions.

👉 Bottom line: You can list without a UPC, but you can never ship without an FNSKU.

Best Practices for Managing FNSKUs in 2025

1. Integrate FNSKU at Manufacturing Stage

   • Ask your supplier to print FNSKUs directly on packaging.

   • Saves on Amazon labeling fees.

2. Use Thermal Printers for DIY Labels

   • Invest in a thermal printer (like Rollo or Zebra) for professional, scannable labels.

3. Cover All Non-Amazon Barcodes

   • Prevent mis-scans by covering manufacturer UPCs.

4. Audit Inventory Regularly

   • Check that Amazon is correctly tracking your stock by FNSKU.

5. Plan for Scalability

   • If you plan to sell in retail stores, you’ll still need GS1 UPCs in addition to Amazon FNSKUs.

Conclusion

The FNSKU barcode may seem like just another Amazon requirement, but it’s actually a powerful tool that protects sellers. It ensures your inventory is not mixed with competitors, safeguards your brand reputation, and guarantees that sales are credited to your account.

As an Amazon FBA seller in 2025, mastering FNSKUs is essential. Whether you’re just starting with GTIN exemptions or scaling a full private-label brand, make FNSKU labeling part of your standard operations.