SKU (Stock Keeping Unit)

A SKU (Stock Keeping Unit) is the identifier you control inside your own systems and inside Seller Central. It is distinct from the ASIN Amazon assigns: ASINs are the catalogue, SKUs are your inventory ledger.

SKU conventions

A workable SKU scheme encodes business meaning in a compact string:

[BRAND]-[CATEGORY]-[SIZE]-[VARIANT]-[CHANNEL]
ACME-MUG-12OZ-BLU-FBA

Avoid SKUs that depend on a database to interpret (PROD-00482-7). The whole point of a SKU is that a human can pick it out of a packing list.

Why multiple SKUs per ASIN

Common reasons a seller maps two or more SKUs to one ASIN:

• FBA + FBM split: one SKU fulfilled by Amazon, a backup SKU fulfilled by the seller.
• Multi-warehouse: same ASIN stocked in EU vs. UK vs. US.
• Lot tracking: different production batches for expiry-sensitive goods.
• A/B price testing on FBM: distinct SKUs at different price points (FBA does not allow this).

SKU vs. FNSKU

If the SKU is sent into Amazon FBA, Amazon assigns it an FNSKU — the barcode the fulfilment centre uses to pick the right unit. SKU is yours, FNSKU is Amazon's pick-path.

Common mistakes

• Reusing a deleted SKU. Old reviews, returns, and refunds can still attach; reporting becomes ambiguous.
• Renaming live SKUs. Breaks every report, dashboard, and ad rule that referenced the old name. Add a new SKU, deplete the old, retire.
• Not separating FBA vs. FBM SKUs. Mixing fulfilment methods under one SKU makes margin analysis impossible — FBA fees and FBM shipping costs are entirely different.