Labelling products correctly before sending them to Amazon FBA is one of the most operationally critical tasks in the wholesale fulfilment process. The FNSKU barcode label is the single piece of information that connects your physical product unit to your seller account inside Amazon’s fulfilment centre. When it is missing incorrectly applied low quality or placed in the wrong position Amazon cannot process your unit — and the consequences range from a relabelling fee to a complete rejection of the affected units at your cost. For wholesale FBA sellers handling tens or hundreds of units per shipment applying labels correctly every single time is not just a compliance task — it is a core business operation.

We are Brandhunterz Ltd — a UK registered wholesale sourcing company (Company No: 15342697) — and in this complete guide we explain exactly what the FNSKU barcode is how to generate and print it how to apply it correctly to every product type and all the additional prep labelling requirements that apply to specific product categories including expiry date labels suffocation warnings and hazard labels.

What is an FNSKU Barcode and Why Does Amazon Require It

FNSKU stands for Fulfilment Network Stock Keeping Unit. It is a unique barcode identifier that Amazon generates specifically for your seller account and your specific product listing. Unlike a standard EAN or UPC barcode — which identifies the product regardless of who is selling it — the FNSKU identifies the product AND the specific seller who sent it to the fulfilment centre. This distinction is critical for two reasons:

Why FNSKU Matters	What Happens Without It
Links your physical unit to your seller account	Amazon cannot credit the sale to your account — revenue lost or incorrectly attributed
Enables dedicated inventory tracking per seller	Without FNSKU your stock may be co-mingled with other sellers’ inventory — quality control lost
Enables accurate received quantity reconciliation	Amazon cannot confirm your sent quantity was received — discrepancies become unresolvable
Required for FBA receiving process to complete	Units without readable FNSKU are held — relabelling fee applied or units returned at seller cost

Step 1 — How to Generate FNSKU Labels in Seller Central

FNSKU labels are generated directly inside your Amazon Seller Central account — they are unique to your seller account and cannot be reused across different products or different sellers. Here is exactly how to generate and download your FNSKU labels:

Step 2 — Choosing the Right Label Printer

The quality of your FNSKU labels is directly determined by your printing setup. Poorly printed labels cause receiving failures that delay your stock going live and can trigger relabelling charges. Here is a comparison of the two main printing options for FBA sellers:

Printer Type	Pros	Cons	Recommended
Thermal label printer	Fast — no ink costs — sharp consistent barcodes — purpose-built for label printing	Higher upfront cost — thermal label rolls needed	✅ Best option
Laser printer with label sheets	Good print quality — uses standard 30-up A4 label sheets — most sellers already own one	Slower than thermal — toner cost — sheet misalignment risk	✅ Good option
Inkjet printer with label sheets	Low cost — widely available	Ink can smudge — barcode quality variable — risk of scan failures at warehouse	❌ Not recommended

Step 3 — How to Apply FNSKU Labels Correctly

Printing a high-quality FNSKU label is only half the task — applying it correctly to every unit is equally important. A perfectly printed label applied to the wrong location or applied over a curved surface will fail scanning at the fulfilment centre just as surely as a poor-quality print would. Here is the exact application process:

FNSKU Labelling on Specific Product Types

Standard boxed retail products are the easiest to label — the FNSKU goes flat on the back panel over the original barcode. But wholesale FBA sellers frequently encounter product types that require different labelling approaches. Here is how to handle the most common non-standard cases:

Product Type	Labelling Approach
Round bottle or tube — no flat surface	Place in a sealed poly bag — apply FNSKU label flat on the outside of the bag — cover poly bag itself with label not the bottle inside
Product in shrink wrap — barcode underneath wrap	Apply FNSKU to the outside of the shrink wrap over the original barcode position — do not remove shrink wrap
Multi-unit set sealed in poly bag	Apply FNSKU to the outside of the sealed poly bag — all individual unit barcodes inside the bag do not need to be covered
Product in retail window box — barcode on back	Apply FNSKU directly over original barcode on the back of the retail box — standard application
Bubble-wrapped fragile product	Apply FNSKU label to the outside of the bubble wrap — never inside the wrap — must be readable on the outermost surface
Product with multiple barcodes on packaging	Cover every scannable barcode on the entire packaging with FNSKU or opaque sticker — leave only FNSKU readable

Additional Labelling Requirements Beyond FNSKU

The FNSKU label is required on every unit — but certain product types require additional labels or markings beyond the FNSKU. These additional requirements are enforced by Amazon to meet safety legal or operational standards and failing to apply them correctly is treated the same as any other packaging non-compliance:

Expiry Date Labels

Food grocery supplement and health products must display a clearly readable expiry date in the format MM-YYYY on the outermost surface of the unit. If the manufacturer’s expiry date is printed in a format Amazon does not accept — such as a Julian date code or a best before printed on the base without a clear month-year format — you must apply an additional sticker label showing the expiry date in the correct format. The date must be visible without opening any packaging and must show at minimum 90 days remaining from Amazon’s receiving date.

Suffocation Warning Labels

Any poly bag with an opening larger than 12.7cm must carry a suffocation warning label. The warning must state that the bag is not a toy and should be kept away from babies and children. The text must be in English and must be clearly readable — either printed directly on the bag or applied as a sticker label. Pre-printed poly bags with suffocation warnings already included are widely available and are strongly recommended for wholesale sellers who regularly use poly bags as part of their prep process.

Sold as Set — Do Not Separate Labels

Products that consist of multiple items sold together as a single unit must be labelled with a Sold as Set — Do Not Separate label on the outer packaging or poly bag. This prevents warehouse staff from separating the components and selling them individually. The label must be clearly visible and must appear on the outermost surface of the bundled unit.

Lithium Battery Hazard Labels

Products containing lithium batteries — whether built-in or sold with batteries — must carry the appropriate UN hazmat label on the shipping box. The specific label required depends on whether the batteries are lithium-ion or lithium-metal and whether they are installed in the device or packed separately. UN3481 applies to lithium-ion batteries installed in equipment. UN3091 applies to lithium-metal batteries installed in equipment. These labels must appear on the outer shipping box — not on the individual product unit — and must meet IATA dangerous goods labelling specifications.

The Complete FNSKU Labelling Quality Checklist

Labelling Quality Check	Required
FNSKU label generated in Seller Central — correct ASIN confirmed	✅ Yes
Labels printed at 100% scale — not scaled to fit — on laser or thermal printer	✅ Yes
Sample label scan-tested before bulk application — reads correct FNSKU code	✅ Yes
Each unit has exactly one FNSKU label — no duplicates	✅ Yes
FNSKU label applied on flat surface — no curves or seams	✅ Yes
All original barcodes on unit fully covered by FNSKU or opaque sticker	✅ Yes
Label applied on outermost surface — not inside poly bag or under wrapping	✅ Yes
Label lies completely flat — no bubbles wrinkles or lifted edges	✅ Yes
Expiry date label applied to food supplement or health units where required	✅ Yes
Suffocation warning on all poly bags with opening over 12.7cm	✅ Yes
Sold as Set labels on all multi-component bundles	✅ Yes
All labelling checks passed — units ready to pack into shipping boxes	✅ GO

Conclusion — Label Correctly Every Time Without Exception

FNSKU labelling is one of the few tasks in Amazon FBA wholesale where there is no room for approximation. The label is either correct or it is not — and the consequences of an incorrect label fall entirely on the seller. Build a consistent labelling workflow using the correct printer settings the scan-test process and the pre-boxing count check and apply it without exception to every unit in every shipment regardless of how routine the process feels.

Find your next wholesale brand through our Brands Directory. Research every product with Keepa. Confirm your margin with AMZScout. And label every unit correctly before every shipment using the process in this guide.