A purchase order, usually shortened to PO, is the document a buyer issues to a supplier to commit to purchasing specified goods or services at agreed terms. It is the first externally binding step of the procure-to-pay chain, and the reference against which everything downstream is checked.
A complete PO carries a unique PO number, the supplier identity, line-by-line descriptions with quantities and unit prices, the delivery address and date, and the payment terms. In contract terms it is an offer: it becomes a binding agreement once the supplier accepts it, whether explicitly or by beginning performance.
The PO number matters more than any other field, because it is the key everything else is matched on. The supplier is expected to quote it on the invoice, the warehouse records receipts against it, and accounts payable uses it to link the three documents together. When that number is missing, mistyped or refers to a closed PO, the match fails and the invoice drops into manual handling, where it costs several times more to process.
A PO is not a purchase requisition, which is the internal request that precedes it, and it is not an invoice, which is the supplier's claim for payment afterwards. The three documents are created by different parties at different moments, which is precisely why comparing them detects errors that no single document reveals.
Where a PO exists, three-way matching can verify the invoice against the commitment and the goods received note automatically. Phacet reads the PO reference from the invoice itself through invoice data extraction, so a missing or malformed number becomes a flagged exception rather than a silent routing failure. See the accounts payable hub.
