Purchase order (PO)

A purchase order is the customer's side of the deal: their reference number, the items, quantities, prices, delivery date and payment terms. Larger buyers will not pay an invoice that does not match a PO, so it is the document your payment depends on.

Read it against your quotation before you deliver. A term you did not agree to — a longer payment period, a penalty for late delivery — is easier to fix before the goods leave than after.