Inventory Labeling: SKUs, Barcodes, and FBA Rules | Inventory Hero
·5 min readAmazon FBA
Inventory Labeling: SKUs, Barcodes, and FBA Rules
Inventory labeling gives every unit an identity you can track. SKUs, UPC vs FNSKU, lot and location labels, and the FBA rules that prevent stranded stock.
Inventory labeling is applying scannable identifiers to your products so each unit can be tracked accurately. It works in layers: an internal SKU you assign, the product's barcode (a UPC or GTIN), and, for FBA, an Amazon FNSKU label. Additional labels like lot or batch numbers, expiration dates, and warehouse location codes add traceability. Good labeling is the foundation of accurate inventory records.
What is the difference between a UPC and an FNSKU?
A UPC (or GTIN) is the manufacturer's product barcode that identifies the product itself, shared by all sellers of that item. An FNSKU is Amazon's own barcode that identifies your specific units within FBA. Labeling your FBA units with an FNSKU means Amazon always ships one of your units rather than pooling them with other sellers', which protects you from counterfeit and quality issues in a shared pool.
Andrew Erickson is the founder of Inventory Hero. He has spent years working with Amazon FBA sellers on demand forecasting, restock planning, and the cash flow side of running a private-label brand. Inventory Hero exists because every spreadsheet-based inventory system he tried eventually broke — usually right before Q4.
For most sellers, yes, you should label with an FNSKU (Amazon barcode) rather than commingle by manufacturer barcode. FNSKU labeling keeps your units traceable and separate from other sellers', which protects your account from problems caused by another seller's stock. You can apply the labels yourself, have your supplier or prep center do it, or pay Amazon's per-unit labeling service. Follow Amazon's exact prep and label requirements to avoid stranded or refused units.
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Inventory labeling gives every unit a scannable identity so you can track it accurately across your operation. The short version: it works in layers (your internal SKU, the product barcode, and Amazon's FNSKU for FBA), labeling FBA units with an FNSKU keeps them yours and traceable, and lot, expiration, and location labels add the traceability some products need. Below are the layers, the FBA rules, and how to label well.
Inventory labeling is not one thing; it is a stack of identifiers, each with a job:
Internal SKU. The code you assign to identify a product in your own systems. It should be consistent, meaningful, and unique, because it is how you refer to the product everywhere.
Product barcode (UPC / GTIN). The manufacturer's barcode identifying the product itself, shared by everyone who sells that item. It is what Amazon matches to a listing.
Amazon FNSKU. Amazon's own barcode identifying your specific units inside FBA. This is the layer that keeps your stock yours.
Most sellers need all three: the SKU for their systems, the UPC for the listing, and the FNSKU for FBA units.
The distinction that trips sellers up is UPC versus FNSKU:
A UPC (or GTIN) identifies the product, and is shared by all sellers of that item. Validate it before you build the listing with the UPC barcode validator, because an invalid or mistyped code causes listing errors down the line.
An FNSKU identifies your units within FBA, uniquely to you.
Labeling your FBA units with an FNSKU means Amazon always ships one of your units, not a pooled one from another seller. Skipping it, and letting Amazon track by manufacturer barcode, means commingling, which exposes you to another seller's counterfeit or quality problems. For almost every brand and private-label seller, FNSKU labeling is the right default.
Beyond identity, some products and operations need labels that trace a unit's history:
Lot or batch numbers tie a unit to a production run, which matters for recalls and quality issues, and is required in some categories.
Expiration dates are mandatory for consumables and other dated goods, and Amazon enforces them for FBA.
Location or bin labels identify where stock sits in your own warehouse, so picking and counting are fast and accurate.
You do not need all of these for every product; add the traceability your category, your compliance requirements, or your warehouse actually needs. A consumables seller lives on expiration and lot labels; a simple hard-goods seller may need none of them, just the SKU, UPC, and FNSKU. Match the traceability to the real requirement rather than labeling for its own sake.
For FBA, labeling is not optional polish; it is what gets your stock received cleanly:
Apply the correct FNSKU label to each unit (or eligible case), exactly as Amazon generates it. The two most common stranding causes are both label problems: an FNSKU missing entirely (so the unit is received as commingled or not matched to your listing) and a label the scanner cannot read (obscured, low-quality print, or placed over the manufacturer barcode). Cover the manufacturer barcode with the FNSKU and use clean labels to avoid both.
Follow prep requirements, poly bagging, bundling, and category-specific rules, alongside the label.
Choose who labels. You, your supplier, or a prep center can apply FNSKU labels, or you can pay Amazon's per-unit labeling service; a prep center is often worth it at volume.
Getting labeling right at the packing table prevents the receiving problems covered in inbound shipments; getting it wrong strands inventory before it ever sells.
Your internal SKU is the one label you fully control, and a little discipline pays off as the catalog grows:
Make it meaningful but stable. A SKU that encodes product, variation, and maybe a supplier code is readable at a glance, but do not pack in anything that changes (price, season) or you will be renaming SKUs constantly. A workable format is brand-product-variant-pack, for example WGT-MATTE-BLK-1PK: five stable fields you can read at a glance, none of which change, so historical sell-through stays clean.
Keep it unique and permanent. One SKU per distinct sellable unit, never reused, so history stays clean. Reusing an old SKU for a new product corrupts your reporting.
Be consistent. Pick a format (segments, separators, length) and apply it to every product, so SKUs sort and filter predictably in a spreadsheet or system.
Avoid ambiguous characters. Skip characters that are easy to misread or that break barcodes and file exports.
Good SKU hygiene sounds trivial until you have hundreds of products; then it is the difference between reporting you can trust and a tangle you fight. Set the convention early and hold it.
Inventory labeling gives every unit a scannable identity across layers, your internal SKU, the product UPC, and Amazon's FNSKU, plus lot, expiration, and location labels where needed. For FBA, FNSKU labeling keeps your units yours and traceable, and following Amazon's exact label and prep rules is what keeps stock from being stranded or refused. Good labeling is the foundation of the accurate records every other decision depends on; see inventory accuracy and commingled inventory. Accurate labels feed accurate counts and reorder triggers, so for the full replenishment system see FBA restock planning.