The unique SKU of the item being revised. A SKU (stock keeping unit) is an identifier defined by a seller. SKU can only be used to revise an item if you listed the item by using AddFixedPriceItem or RelistFixedPriceItem, and:
1) You set Item.InventoryTrackingMethod to SKU at the time the item was listed; or
2) You are modifying a multi-variation listing, and the SKU identifies one of the variations. (In this case, if InventoryTrackingMethod was set to ItemID, then you also need to specify ItemID in the request.)
(These criteria are necessary to uniquely identify the listing or variation by a SKU.)
In the ReviseInventoryStatus request, if the listing has InventoryTrackingMethod set to SKU, then either ItemID or SKU is required. If both are passed in and they don't refer to the same listing, eBay ignores SKU and considers only the ItemID.
If the listing has variations and InventoryTrackingMethod is set to ItemID, then ItemID and SKU are both required.
In the response, SKU may be returned as an empty element if it was not defined on the listing.
See the
Field Index to learn which calls use SKU.