By default, all Buyer properties are not permitted to have a negative stock level. However, if your property allows this, you can do this via [Business Settings].
Note: this action can only be completed by an Account Administrator in your Organisation.
Please follow the below steps.
1. From [Dashboard], go to [System] [Purchasers].
2. On the right-hand side pop up menu, click on [Business Settings] tab as shown below.
3. Locate [Allow Negative Stock Level], which is the third line from the top of the menu, as below.
4. If the box on the left of 'Allow Negative Stock Level' is not ticked, [tick] the checkbox to enable the 'Allow Negative Stock Levels' function.
Press [Enter] on the keyboard and the change will take immediate effect.