A "purchase order" (or "PO") is a written sales contract between buyer and seller outlining what is being purchased. It will include all details such as the items, quantities, and amounts, and can also include details like payment terms, delivery estimates and any other contractual elements.
No money is due at the receipt of a PO. That will happen when an invoice is sent afterward.
Purchase orders are a lot like proposals or estimates. To create one in LessAccounting, use our "Proposal" option. In fact, you can even change the word "Proposal" to "Purchase Order" or "PO" by going to Settings > Label Translation
Once your customer has approved the PO and plans to pay, simply convert the PO to an invoice using the "Convert to Invoice" button at the bottom of the PO editing screen.