What Is a Purchase Order? (And How It Differs from an Invoice)

What Is a Purchase Order?

A purchase order (PO) is a commercial document issued by a buyer to a seller, formally authorizing a purchase. It specifies the goods or services required, quantities, agreed prices, and delivery terms — before any goods change hands or any work begins.

Think of it as the buyer's formal commitment: "I want to buy this, at this price, delivered here, by this date." Once the seller accepts, both parties are bound to those terms. It is the foundation of any formal procurement process.

What Is an Invoice?

An invoice is issued by the seller after the goods or services have been delivered. It requests payment for what was provided and typically references the original purchase order number.

Purchase Order vs Invoice — Side-by-Side Comparison

When to Use a Purchase Order

Purchase orders are used when:

• You are buying goods or services from a supplier for your business
• You need a formal, traceable authorization (for audit, compliance, or internal approval)
• You are buying on credit terms (the PO commits you before payment is made)
• You want to lock in prices on items that may change in cost
• Multiple people in your organization have approval authority (the PO requires sign-off before ordering)

What Goes in a Purchase Order — 10 Fields

1. PO Number (unique, sequential)
2. PO Date
3. Buyer's name, address, and contact
4. Seller's name, address, and contact
5. Delivery address (if different from buyer's address)
6. Description of goods or services
7. Quantity
8. Unit price and total
9. Required delivery date
10. Payment terms (Net 30, etc.) and any special conditions

How to Create a Purchase Order in 5 Steps

1. Choose a template. Start with a free PO template from Templix AI — all fields pre-labelled.
2. Assign a PO number. Use a sequential system: PO-2026-001, PO-2026-002. Never reuse numbers.
3. Fill in buyer and seller details. Include full legal name, address, and contact information for both parties.
4. List the items. Each line item: description, quantity, unit price, total. Be specific — vague descriptions cause disputes.
5. Send for approval and confirmation. Get internal sign-off if required, then send to the supplier. Keep a copy; the supplier's confirmation (written or via return email) makes it a binding agreement.

PO Number — What It Is and How to Format It

A PO number is a unique reference number that tracks the purchase order through your procurement and accounting system. When the seller invoices you, they quote the PO number — making it easy to match invoices to purchase orders during payment processing.

Common formats:

• PO-2026-001 (year + sequential)
• PO-CLIENTNAME-001 (client code + sequential)
• 20260814-001 (date + sequential)

Frequently Asked Questions

Is a purchase order legally binding?

Yes, once the seller accepts it (by acknowledgment, email confirmation, or beginning to fulfil the order). At that point it is a legally enforceable contract.

Do small businesses need purchase orders?

Not always — but any business buying on credit or needing a paper trail for compliance should use them. For small ad-hoc purchases, a simple email confirmation may suffice.

What happens if the supplier ships something different from the PO?

You have the right to reject non-conforming goods and request replacement or a credit note. The PO is your proof of what was agreed.

Can I cancel a purchase order?

Before the supplier has started work or shipped goods, yes — typically without penalty. After acceptance, cancellation may trigger a restocking fee or cancellation charge depending on your terms.

What is a blanket purchase order?

A blanket (or standing) PO sets up a recurring purchase arrangement — for example, "supply 500 units per month for 12 months at £X per unit." Reduces admin for repeat purchases from the same supplier.

For more ready-to-use layouts, check out our collection of free document templates to speed up your paperwork.