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When using File Exchange to create active listings, the SKU (stock keeping unit) field is not required. Your listings are managed by the eBay item number given to the listing. A spreadsheet can be uploaded to eBay through Seller Hub or via server using XML.
On the other hand, when using the Merchant Integration Platform (MIP), you are uploading inventory products that are identified and accessed by the product identifier that you provide. This is how most ecommerce sites handle inventory, so the method makes it easier to list products across multiple platforms and on your own website. eBay will still assign an item number when you list your inventory item for sale, but you can also manage inventory by the SKU that you assign through MIP.
