NetSuite has a feature allowing users to invoice the inventory items even if they are not fulfilled. This feature is applicable in the cases where invoice in advance of fulfillment feature is not enabled.
When a sales order is saved with 2 inventory items, it will show only fulfill button. If any one item out of 2 is fulfilled then invoice button will be shown on sales order to invoice the fulfilled item. With this feature enabled, if user clicks on invoice button on sales order, new invoice will show both the fulfilled and unfulfilled items.
