What if a Sales Order is confirmed and products are delivered but no invoice is required. Then this leaves a Sales Order in the "Sale to invoice" state with only two options. (1) Create an invoice of zero (unacceptable). (2) Cancel the Sales Order (doesn't seem right). What is the better alternative?
For example, a customer orders a repair, then products are delivered for the repair, then by the nature of the repair it is determined to be under warranty and therefore no invoice will be made.