Once you have determined an inventory shortage exists you can place a PO from the Sales Order screen. Click on Create Invoice, then Purchase Order. You can create a PO for selected items or all line items on the Sales Order.
When the shipment is received from the PO you will process the backordered items on the Sales Order.
Onc way to monitor this is to print the Open Sales Order report by Customer or Item. Zoom into the Sales Order, click Create, then Invoice.
Once the backorder quantities are fulfilled the Sales Order will display in red in the header “Invoiced In Full”. Also the Sales Order is marked as Closed. The closed column “Clsd” will have a check mark in each column that has it’s qty totally fullfilled.