*The Allow negative feature helps if the item inventory refers to the situation when an stock count less than zero of the item, it will allow to do the sales.
Real Time Scenario: If the item stock is less than zero ,If we enabled the configuration for sales, it will allow do the sales with the negative stock. For example :Cold coffee item has "0"Stock, but sales has been done for 10 Quantity ,It will go under negative "-10"Quantity stock.
To Enable the Configuration:
Go to Settings->Configuration-> Sales Configuration->" Allow Negative stock in Sales" as "Yes "->Update.
For Example: Taking zero stock item for the sales , Item name "Green Tea" Regular Stock "0"
The item called "Green Tea" done the sales for "10" Quantity with zero stock.
The item which has Zero stock , after that sales done quantity will go under negative quantity .
Item name "Green Tea" which done sales for 10 quantity with zero stock ,which goes under the negative stock "-10"quantity.