Inventory tracking is available only in QuickBooks Plus.
The inventory as of date is the date you start tracking the quantity on hand of an inventory item in QuickBooks.
How you choose the as of date depends on what you're doing:
You can only use an inventory item in transactions that are dated after the item’s inventory as of date. For example, you create an inventory item and start tracking the quantity on hand on December 1. If you try to use that item on an invoice dated November 30, QuickBooks doesn’t let you save the invoice because the invoice date comes before the date you started tracking that item’s quantity on hand.