First enable System Option 80:

▪Use menu path: Go to the System ribbon menu > System Preferences  > System Options tab  >

Scroll down to System Option # 80 - "Prevent oversell of items". Check this option to be available in Inventory File Maintenance.

 

Next go to the Inventory ribbon menu:

 

1.Find desired inventory item.  
2.Click the box to check it next to Allow Oversell.  
3.Click the Apply button now the oversell restriction is bypassed for that item.
4.Click OK when done with item updates.