Glossary
What is the difference between a purchase order and an invoice?
By Tim White · Last updated
A purchase order (PO) is sent by the buyer to order goods or services, before anything is delivered. An invoice is sent by the seller to ask for payment, after the goods or services are provided. The PO says what was agreed; the invoice says what is owed. They cover the same order from opposite sides.
Who sends what, and when
The buyer writes the purchase order first: what they want, how much, and the agreed price. The seller fulfills it, then sends an invoice referencing that same order. So the PO comes before the work and the invoice comes after.
Why the pair matters at payment time
Before paying, most finance teams check that the invoice matches the purchase order, same quantities, same prices. A mismatch means an overbill, a partial delivery, or a data-entry slip. This check is only as good as the numbers on the invoice.
That is where verified extraction helps. InvoiceJet turns the invoice into structured line items and totals, each with a confidence level and a citation to the source on the document, so the numbers you match against your PO are ones you can trust.
Commonly confused with a quote
A purchase order gets mixed up with a quote and a sales order, and the three sit at different points in the deal. A quote is the seller's price estimate, non-binding, sent to win the work. The purchase order is the buyer's commitment to that price. A sales order is the seller's internal confirmation that they will fill it. Only the invoice, which comes last, asks for money.
Common questions
Does a purchase order guarantee payment?
No. A PO authorizes an order; payment happens after the invoice is received, checked against the PO, and approved.
What is a PO number on an invoice?
A PO number is the reference to the purchase order that authorized the spend. Printing it on the invoice lets the buyer match the bill back to what was agreed, which is the first step of invoice approval.
Can you invoice without a purchase order?
Yes. Many small purchases and services are billed with no PO at all. Some buyers require one above a set amount, in which case a non-PO invoice is routed for extra approval.
Sources
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