The pick slip can be printed in bin location sequence, giving the picker the shortest route for finding the items. The picker should mark each item that is shipped complete and note any items that can't be shipped. These items will have to be backordered. The packer keeps copies two and three for a packing list to accompany the shipment, and returns the original document, with all his hand written notes, to the accounting department. The invoicing data entry operators will use the document to confirm the shipment, thereby creating an invoice. The shipment doesn't need to wait for the invoice, it is mailed later in the day.