The most common SKU vs UPC barcode mistake is printing the number that is convenient instead of the number the receiving system expects. A label can scan cleanly and still be wrong if it encodes an internal SKU where a retailer, marketplace, or fulfillment workflow needs a different identifier.
The short answer: print your SKU for internal inventory, print a GS1-based UPC or EAN for retail product identification when required, and print Amazon ASIN or FNSKU values only from the Amazon workflow that tells you to use them. Do not invent marketplace or retail identifiers in a label generator.
Definitions before you print
| Term | Plain-English meaning | Typical label use |
|---|---|---|
| SKU | A code your business creates for internal tracking. | Inventory, pick lists, shelf labels, POS systems you control. |
| UPC | A 12-digit retail barcode symbol commonly used in North America. | Consumer product labels for retail checkout. |
| EAN | A retail barcode family commonly used outside North America. | Consumer product labels for global retail channels. |
| GTIN | The GS1 product identifier number behind retail product identification. | The data encoded in UPC, EAN, and some other GS1 barcode carriers. |
| ASIN | Amazon Standard Identification Number for an Amazon catalog listing. | Amazon catalog reference, not normally the label value you invent yourself. |
| FNSKU | Amazon fulfillment identifier used to track seller inventory in FBA. | Amazon barcode labels when Seller Central requires Amazon barcode tracking. |
SKU is your internal code
A SKU is created by your business. It can describe category, size, color, supplier, or location in a way your team understands, such as TEE-BLK-M or CLEAN-12OZ-00482. Shopify explains that SKUs are unique codes for internal tracking, while barcodes are universal identifiers used across retailers and sales channels: Shopify barcode FAQ.
For private workflows, encoding the SKU can be exactly right. A shelf label, bin label, asset label, or backroom product label can scan into your inventory system and look up the record. The risk begins when the label leaves your system and another party expects an official product identifier.
UPC, EAN, and GTIN are retail identity terms
A UPC or EAN is the scannable barcode symbol seen on retail products. A GTIN is the identifying number used in the GS1 system. GS1 US describes the UPC as a symbol encoded with a GTIN and scanned at point of sale to identify an item and look up price: GS1 US guide to UPCs.
Do not print a UPC-looking barcode around a random internal number. If a retailer or marketplace asks for a GS1 barcode, get the identifier through the correct GS1 process. GS1 US also explains that each product variation needs its own barcode, such as separate sizes, colors, styles, or packages: GS1 US get a barcode.
ASIN and FNSKU are Amazon workflow terms
An ASIN identifies a product listing in Amazon's catalog. An FNSKU is tied to fulfillment tracking for a seller's FBA inventory. Amazon's public FBA labeling PDF describes FNSKU as an identifier used by Amazon fulfillment centers to identify individual offers of a specific ASIN, and says labels include FNSKU, product name, and condition: Amazon FBA product label PDF. That PDF is old and says to visit Seller Help for the latest version, so treat it as background and verify current account instructions before printing.
Amazon also publishes public seller-forum guidance saying all units sent to Amazon require a barcode, and that Amazon uses manufacturer barcodes, Amazon barcodes, and Transparency barcodes in different situations: Amazon Seller Central forum guidance. For inventory shipped on or after March 31, 2026, Amazon says Brand Representative sellers may use manufacturer barcodes for products that already have them, while resellers who are not Brand Representatives must use Amazon barcode stickers even when a manufacturer barcode exists: Amazon Seller Central March 31, 2026 announcement. Your current Seller Central shipment, product, and barcode preference settings are the authority for a live FBA job.
Do not print this until you know
- doneWho will scan itYour own team, a retail checkout, a distributor, Amazon, or another marketplace.
- doneWhich system owns the valueYour spreadsheet, POS, GS1 account, Amazon listing, or shipping workflow.
- doneWhich code type is requiredCode 128, UPC-A, EAN-13, QR code, Amazon barcode, or another specified format.
- doneWhether variants are separateSize, color, condition, bundle, and package changes may require distinct identifiers.
- doneWhether old barcodes must be coveredMarketplace and fulfillment workflows often reject multiple visible product barcodes.
Marketplace requirements change. Before printing production labels, open the current order, listing, shipment, or prep page inside the official seller account and confirm the exact barcode value, label size, placement, and coverage rules.
If you still need to choose the scannable format after choosing the identifier, use Code 128 vs QR Code Labels. If the values come from a spreadsheet, clean them first with the barcode label data cleanup checklist.
Write the exact source of each identifier in your spreadsheet before designing the label: internal SKU, GS1 GTIN, Amazon value, or another system-owned code.