What is a purchase order?
A purchase order tells a supplier exactly what a buyer wants to buy and on what terms. It kicks off a purchase, sets shared expectations on price, quantity, and delivery, and becomes a legally binding contract once the supplier accepts it.
Because the buyer issues it, a PO is the mirror image of a sales order, which the seller sends back in response. Clear paperwork keeps the purchase order process predictable for both sides.
Key characteristics
- A unique PO number: every PO carries an identifier used to track it and later match it against the delivery and the invoice, known as the three-way match.
- Agreed terms in writing: item descriptions, quantities, unit and total prices, payment terms, shipping method, and the expected delivery date.
- A binding commitment once accepted: the PO becomes a contract when the supplier accepts, which protects both sides and creates a records trail against billing and vendor fraud. Those occupational fraud losses carry a median loss of $104,000 per case, and a documented PO supports the three-way match that helps catch them (ACFE, Occupational Fraud 2026: A Report to the Nations).
- Can be generated automatically: modern inventory systems draft POs from reorder points, using auto purchasing instead of manual entry.
- A source of accurate records: POs keep purchasing, budgeting, and stock counts aligned. When those records drift, the inventory distortion cost of out-of-stocks plus overstocks reached $1.7 trillion globally in 2026, equal to 6.2% of global retail sales (IHL Group 2026 Inventory Distortion Study).
Example
Picture a craft cold-brew roaster that needs new packaging. It creates a PO for 5,000 glass bottles at an agreed unit price and sends it to its bottle supplier. The supplier accepts, ships the bottles, and the roaster matches the delivery and invoice back against the PO number.
Handling this by hand eats up hours, which is why many teams are automating purchase orders. Ardent Partners’ 20th-annual State of ePayables research, based on 204 accounts payable (AP) professionals and their organizations, names automation a top priority for accounts payable teams in 2025 and beyond. One Fishbowl food-production customer, COYO, cut the time to place orders from one to two days down to two to three hours.
Related terms
- sales order processing: how sellers receive, confirm, and fulfill incoming customer orders.
- procurement management: the wider process of sourcing and buying goods and services.
- order management system: software that tracks orders from purchase through fulfillment.
FAQ
What is the difference between a purchase order and an invoice?
The buyer issues a PO to request goods before the purchase, while the supplier issues an invoice to request payment after filling the order.
Is a purchase order legally binding?
A PO is not binding on its own, but it becomes a legally binding contract once the supplier accepts it.
Who creates a purchase order?
The buyer creates and sends the purchase order, and the seller responds with a sales order or an order confirmation.