A purchase order (PO) is a commercial document a buyer issues to a supplier that commits to buying specified goods or services at agreed quantities, prices, and terms. It is the formal instruction that initiates a purchase and, once accepted, becomes a binding agreement.
A purchase order is the buyer's formal commitment to buy. It states what is being ordered, in what quantity, at what price, and with what delivery and payment terms, and it carries a unique reference number used to track the transaction through confirmation, delivery, and invoicing. On the buyer's side, the PO authorizes the spend; on the supplier's side, it is the instruction to fulfill.
The purchase order sits at the center of the procurement cycle. It follows any request for quotation and negotiation, it is answered by the supplier's order confirmation, and it is later matched against the delivery note and invoice to verify that what was ordered is what arrived and what is billed. This three-way matching, PO against delivery against invoice, is a foundation of procurement control, and each link in it depends on the purchase order as the reference.
A manufacturer's procurement team raises a purchase order in SAP for raw materials, sends it to the supplier, and receives an order confirmation in response. The PO number links every subsequent document: the confirmation, the delivery note, and the invoice.
On the supplier's side, an incoming purchase order arrives by email as a PDF using the customer's own part numbers. Sales order automation reads it, matches the customer's numbers to internal SKUs, and creates the corresponding sales order.
The difference is perspective: a purchase order is created by the buyer to order goods, while a sales order is created by the seller to record and fulfill that same order in their system. The same transaction is a purchase order to the buyer and a sales order to the supplier. One document, two viewpoints across the transaction.
Purchase orders are most useful when they carry complete, accurate terms and a reference number that links them cleanly to the confirmation, delivery, and invoice for three-way matching. On the receiving side, automating the conversion of an incoming purchase order into a sales order, including matching customer-specific part numbers, removes a major source of manual effort and error.
The purchase order is the anchor document of the procurement cycle, referenced by every step that follows. Handling it accurately, whether raising it or converting an incoming one into a sales order, keeps the whole order-to-delivery chain aligned.
