When Does Product Inventory Change (Decrease) During The Ordering Process? How Can An Administrator Control The Inventory Change?Michael Cristancho·Magento Certified Solutions Specialist·October 10, 2014·1 min read Share When does product inventory change (decrease) during the ordering process? How can an administrator control the inventory change? Product inventory is decremented when an order is submitted. An administrator can control the inventory change by altering the product’s inventory with Manage Products.