Purchase Order vs Invoice: What’s the Difference?
A purchase order and an invoice move in opposite directions between the same two parties — the buyer issues the PO, the seller issues the invoice — and understanding that flow clears up most of the confusion between them.
Who sends what
A purchase order is created and sent by the buyer, authorizing a purchase before it happens. An invoice is created and sent by the seller, requesting payment after the goods or services are delivered (or due). They document the same transaction from opposite sides of it.
How they connect
In a PO-based workflow, the seller references the buyer’s PO number on the invoice, and the buyer’s accounts payable team checks that the invoice matches the original PO — same items, same price — before releasing payment. This "PO matching" is largely why invoices to companies using POs get rejected if the number is missing or the amounts don’t align.
When a PO isn’t involved
Most small transactions — freelance work, small-business services, direct-to-consumer sales — skip the PO step entirely and go straight from quote (or no formal quote at all) to invoice. POs mainly show up with larger organizations that have a formal procurement process requiring pre-approval of spending.
FAQ
Can I send an invoice without a purchase order?
Yes, for most clients — a PO is only required if the buyer’s process specifically calls for one. Many small businesses and individual clients never use POs at all.
What if my invoice total doesn’t match the PO?
Flag and explain the difference before invoicing if possible — an unexplained mismatch is one of the most common reasons a corporate accounts payable team delays or rejects payment.
Does a purchase order guarantee I’ll get paid?
It significantly improves the odds, since it represents pre-approved spending, but payment still depends on you delivering as agreed and invoicing correctly against it — a PO isn’t itself a payment.
Do I need a new PO for every invoice?
Depends on the buyer’s process — some POs cover a single purchase, others (called blanket or standing POs) authorize multiple invoices over time up to a set limit. Check with the client which applies.
Put this into practice with a real invoice.
Try the free Invoice GeneratorRelated Guides
- What Is a Purchase Order? A Plain-English Guide
What a purchase order is, how POs work, what they include, and how they differ from quotes and invoices — with a real example.
- Quote vs Invoice: What’s the Difference?
The difference between a quote and an invoice, when each becomes legally binding, and how both fit into your sales workflow — with plain examples.