If a purchase order is broken up into multiple shipments or items are backordered, the PO you create in Heartland Retail will stay open until all items are received. If you are notified by the vendor that items will not ship, you can close lines individually on the PO by selecting the checkboxes next to each item and clicking the "Close Selected Lines" button.
Once all items have been received against the PO or once all unreceived lines have been closed, the PO will close automatically.
Once a PO has been closed, it cannot be reopened.