The Inventory tab stores Inventory related options for inventory items transferred into QuickBooks Online.
As of Date: The inventory As of Date is the date on which you start tracking the Quantity on Hand of an inventory item in QuickBooks Online. (Inventory tracking is available only in QuickBooks Online Plus.)
Please note that this field is NOT required. If you use the Settings > Advanced > Close the books option in QuickBooks Online, this field date value MUST be greater than or equal to the Close the books Closing date value. If you do not use the QuickBooks Online Close the Books option, you do not need to set this field.