Purchase order format: the fields that keep an order from stalling

A purchase order format looks like paperwork and behaves like plumbing. The PO is what the buyer's finance system matches the delivery note and the invoice against, and if any of the three disagree, payment stops until a human works out why. Most "lost" invoices are really mismatches: a quantity that changed after the order, a price agreed verbally, a PO number nobody quoted.

The format itself is not complicated. It is the same fields every time, filled in the same way.

The purchase order format, field by field

• PO number — unique, sequential, and quoted on every document that follows. This is the key everything else is matched on.
• Order date, and the delivery date or window expected.
• Buyer — legal entity name, billing address, and the delivery address if it differs.
• Supplier — legal entity name and the address on their invoices, not their trading name.
• Line items — description, SKU or part number, quantity, unit of measure, unit price, line total. One row per distinct thing.
• Subtotal, tax treatment, shipping, and the order total in the agreed currency.
• Payment terms — net 30, net 14, or whatever was actually agreed, stated on the order rather than assumed.
• Shipping terms — who arranges carriage and who bears the risk in transit; for cross-border orders name the Incoterm.
• Authorisation — the name of the person approving the order, and their approval limit if your process uses them.

The single most valuable field is the PO number, and the discipline is boring: it must appear on the supplier's invoice. An invoice without it is not a dispute, it is an unmatched document — and unmatched documents wait.

How a PO moves through its life

1. The buyer raises the PO from an agreed quotation and has it approved internally.
2. The PO goes to the supplier, who confirms it — acceptance is what turns it into a contract.
3. Goods or services are delivered, and the delivery note references the same PO number.
4. The supplier invoices, quoting the PO number and matching the lines exactly.
5. Finance runs a three-way match — PO, delivery note, invoice. If all three agree, payment goes out on terms with nobody involved.
6. Any change agreed along the way is recorded as an amended PO, not as an email. This is the step teams skip, and it is the step that causes the mismatch.

Purchase order and invoice are not the same document

The PO is issued by the buyer before the work; the invoice is issued by the supplier after it. The PO says what should happen, the invoice says what did and asks for money. They should be readable side by side: the same line descriptions, the same quantities, the same prices, in the same order. When a supplier restructures the lines on their invoice — bundling three ordered items into one "services" line — the match fails even though the total is right.

If you are on the supplier side, the practical version of this article is short: ask whether the client uses purchase orders before you start, get the PO number in writing, and repeat it on your invoice exactly as written.

Ettex Invoices is built around that matching discipline: line items with quantities, rates, multiple tax rates and discounts, sequential auto-numbering with your own prefix, notes and terms fields where the PO number and payment terms belong, a client book so entity names and addresses stay consistent between documents, statuses from draft to sent to paid, and export as print-ready PDF or as CSV and XLS for your books.

Common purchase order mistakes

• Reusing or restarting PO numbers, which makes the match ambiguous and the audit unpleasant.
• Vague line descriptions — "consulting", "materials" — that cannot be reconciled against a delivery.
• Agreeing a change by phone and never amending the order.
• Leaving tax and shipping treatment implicit, then arguing about the difference on the invoice.
• Raising the PO after the invoice arrives, which defeats the point of the control entirely.

A good purchase order format is one both sides can read the same way, months later, without asking anyone what happened. Same fields, same numbering, same discipline on every order.