Commercial forms guide · Updated 10 October 2026
Purchase order vs invoice: what's the difference?
A purchase order is issued by the buyer to order goods or services; an invoice is issued by the supplier to request payment for them. The purchase order says what the buyer wants and at what price; the invoice says what was supplied and what is owed, and the buyer checks one against the other before paying.
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Purchase order vs invoice at a glance
The difference between a purchase order and an invoice
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| Point of difference | Purchase order | Invoice |
|---|---|---|
| Purpose | Orders goods or services at stated quantities and prices | Requests payment for the goods or services supplied |
| Who issues it | The buyer, to the supplier | The supplier, to the buyer |
| When it is sent | Before delivery, when the order is placed | After delivery, or at the stages agreed |
| What it usually shows | PO number, supplier, items, quantities, unit prices, delivery address and date | Invoice reference, the buyer’s PO number, items supplied, amounts, tax, total and payment terms |
| Legal effect, in plain terms | An offer to buy. Once the supplier accepts it, it can form part of the agreement | A request for payment of what was supplied under that agreement |
Plain-language summary only. The terms that apply depend on what each side agreed; take advice if that matters to you.
Worked example (fictional)
From purchase order to delivery to invoice
Fictional businesses and figures, for illustration only. The tax rate shown is simply the rate entered; it is not advice on what to charge.
1
Purchase order PO-2031 is sent
Northfield Bakery orders 500 cake boxes at £0.38 each (£190.00) and 20 rolls of tape at £2.15 each (£43.00) from Example Packaging Supplies. Subtotal £233.00; tax entered at 20%: £46.60; total £279.60.
2
The goods are delivered
The delivery note shows 480 boxes and 20 rolls of tape. Northfield records that 20 boxes are short.
3
The supplier invoices
Example Packaging Supplies issues invoice INV-7710 quoting PO-2031. It bills 480 boxes (£182.40) and 20 rolls of tape (£43.00): subtotal £225.40, tax £45.08, total £270.48.
4
The invoice is matched to the PO
Northfield compares the invoice with PO-2031 and the delivery note: the prices match the order, and the quantities match what actually arrived. The invoice is approved for payment by Northfield’s own process; the 20 missing boxes stay open on the order.
Matching an invoice to a purchase order
What to check before paying a supplier invoice
Matching means checking that the invoice bills what you ordered, at the agreed price, for what was actually delivered.
Soteriaa’s purchase order generator calculates line amounts, tax and totals from the quantities and prices you enter, and the invoice generator does the same for suppliers. Matching, approval and payment stay with your own process; Soteriaa does not route approvals or check invoices against orders. For the selling side of the same pattern, read quotation vs invoice.
- The invoice quotes your purchase order number.
- Unit prices match the purchase order.
- Quantities match the delivery note, not just the order.
- Any difference (short delivery, substitute items, extra charges) is explained before you pay.
What Soteriaa does and does not do
Soteriaa creates documents from the details and figures you enter. It is not accounting software, it does not process payments or approve purchases, and a “paid” status is only ever recorded by you. This guide is general information, not tax, accounting or legal advice. Commercial tracking (customers and suppliers, issue and due dates, and a payment status you record yourself) is coming but not on sale yet; the generators are free now. See the commercial forms and resources hub.
FAQ
Common questions
Who issues a purchase order and who issues an invoice?
The buyer issues the purchase order to the supplier. The supplier issues the invoice to the buyer.
Should an invoice include the purchase order number?
If the buyer issued a purchase order, quoting its number on the invoice lets the buyer match the two quickly. Many buyers ask suppliers to include it.
Does Soteriaa match invoices to purchase orders?
No. Soteriaa creates purchase orders and invoices from the figures you enter. It does not approve purchases, match documents or process payments.
Write your purchase order now
Free, with calculated totals from the quantities and prices you enter.