We understand that you have created invoices even after the quantity became zero. This usually happens when the ‘Allow Negative Quantity’ option is turned on.
Because of this setting, the system allows billing even when there is not enough stock, which causes the quantity to go into negative. To avoid this concern, please turn off the Allow Negative Quantity option from the settings.
Please refer to the article mentioned below:
For Android: How to prevent adding negative quantities on mobile? - General - Swipe
For Web: How to prevent adding negative quantities on web?
As mentioned, the negative quantity of the product can be automatically adjusted using either of the following methods:
Please refer to articles mentioned below:
1. By creating a Purchase Invoice
How to create a purchase invoice in Swipe Mobile App? - Android - Swipe
2. By manually stocking in the product
How to do manual stock-in of the products on mobile? - General - Swipe