SKU
Also known as: Stock Keeping Unit, Seller SKU, MSKU
A SKU (Stock Keeping Unit) is the seller's own internal identifier for a product variant — distinct from Amazon's shared ASIN — used to track inventory and listings.
A SKU (Stock Keeping Unit), sometimes called the Merchant SKU or seller SKU, is the identifier YOU assign to a specific product you sell. Unlike the ASIN (which Amazon assigns and shares across everyone selling that product) and the UPC/EAN (the global barcode), the SKU is private to your account and entirely your choice of format.
Well-designed SKUs encode useful information — supplier, cost, batch, or condition — so you can manage inventory at a glance, e.g., "WIDGET-BLU-L-SUPPLIERA-0824." Two sellers can list the same ASIN under completely different SKUs, and a single ASIN can even have multiple SKUs in one account (for different conditions or fulfillment channels).
The SKU is the anchor for your operations: restock planning, COGS tracking, and profitability reports key off it. For FBA, each SKU maps to an FNSKU (the FBA-specific barcode), while the public-facing identity stays the ASIN.
A seller lists a blue large t-shirt on a shared ASIN under their own SKU "TSHIRT-BLU-L-001," which encodes color and size so their inventory and COGS reports stay organized even though the ASIN is shared with other sellers.