Disallow Back-order inventory or negative stock

Hi, is it possible for Manager not to allow you to update sales invoice when there is no enough inventory in the warehouse (i.e. i want to disallow NEGATIVE INVENTORY; i don’t want to be able to make sales invoice if i don’t have the inventory)

No, this is not possible, because many users sell inventory before they order it. Search the forum. This has been discussed many, many times. There is also a suggestion in the ideas category about this: Inventory zero warning.