sku can also refer to a unique identifier or code that refers to the particular stock keeping unit. these codes are not regulated or standardized. when a company receives items from a vendor, it has a choice of maintaining the vendor's sku or creating its own. this makes them distinct from global trade item number (gtin), which are standard, global, tracking units. universal product code (upc), international article number (ean), and australian product number (apn) are special cases of gtins.