A purchase order (PO) is a document issued by a supplier to a consumer that authorizes a purchase transaction. When accepted by the supplier, it becomes a contract binding on both parties.  A purchase order includes: the product description, quantities, prices, discounts, payment terms, date of shipment, and terms and conditions. There are three types of purchase orders.  The first type is a regular purchase order, which is used for a one time purchase. The second type is a standing purchase order, which is for goods or services needed from a supplier on a regular basis. The third type is the blanket purchase order, which is a long-term agreement.