Purchase Order vs. Invoice: What’s the Difference?
Purchase orders and invoices are two halves of one transaction: the buyer’s promise to pay, and the seller’s request to be paid. If you sell to companies, you will live with both.
| Aspect | Purchase Order | Invoice |
|---|---|---|
| Who sends what | The buyer issues the purchase order to the seller: “we will buy these items at these prices — PO #4521.” The seller later issues the invoice to the buyer: “here is the bill for PO #4521.” | The PO number is the thread that ties everything together. The buyer’s finance team matches your invoice to their PO before paying — an invoice without the PO number often sits in limbo. |
| Working with POs as a supplier | Ask for the PO number before starting corporate work and put it on every invoice. Check the PO against your quote immediately — quantity, price, scope. Fix discrepancies now, not at invoicing time. | Never invoice above the PO amount without an amended PO or written approval. It is one of the most common reasons invoices get rejected. |
Who sends what
The buyer issues the purchase order to the seller: “we will buy these items at these prices — PO #4521.” The seller later issues the invoice to the buyer: “here is the bill for PO #4521.”
The PO number is the thread that ties everything together. The buyer’s finance team matches your invoice to their PO before paying — an invoice without the PO number often sits in limbo.
Working with POs as a supplier
Ask for the PO number before starting corporate work and put it on every invoice. Check the PO against your quote immediately — quantity, price, scope. Fix discrepancies now, not at invoicing time.
Never invoice above the PO amount without an amended PO or written approval. It is one of the most common reasons invoices get rejected.
Frequently asked questions
Do I need a PO to invoice a company?
Many companies require one — ask upfront. Without it, your invoice may wait weeks while someone manually approves it.
What is PO matching?
The buyer’s three-way match: purchase order vs. goods received vs. invoice. When all three agree, payment is released automatically.
Can small businesses issue purchase orders?
Yes — when you buy from suppliers, issuing your own POs documents your costs and prevents billing surprises.
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