How to Write a Purchase Order

A purchase order is written by the buyer to formally order goods or services and commit to paying for them. To write one, give it a unique PO number, state your details and the supplier's, list the items with quantities and agreed prices, add the delivery and payment terms, and get it approved before you send it. The purchase order locks in what was agreed before any money is owed, which is exactly why finance teams rely on it.

Most freelancers meet purchase orders from the receiving end, when a client asks them to quote a PO number. But if you run a business that buys from suppliers or subcontractors, you may need to write them yourself. Either way, understanding how a good one is built makes the whole buy-and-bill process smoother.

What a purchase order does

A purchase order, usually shortened to PO, is the buyer's formal commitment to a purchase. It says, in effect, "we want these specific things, at these agreed prices, and we agree to pay for them." Once the supplier accepts it, the PO becomes a binding agreement to buy.

Its value is control and timing. The PO is created and approved before the goods or work are delivered, so the spend is authorised up front rather than questioned later. That up-front approval is what lets a supplier begin work with confidence and what lets a finance team pay the eventual invoice quickly, because the commitment already exists in their system. The fuller background is in what is a purchase order.

The details a purchase order needs

A complete purchase order carries a defined set of information, much of it mirroring an invoice but created by the buyer instead of the seller.

A unique PO number, which both sides will reference throughout the transaction and which the supplier will quote on their invoice. The date it was issued. Your details as the buyer: your business name, address, and contact information. The supplier's details. A clear list of the items or services ordered, each with a description, quantity, and the agreed unit price, plus line totals and an overall total. The delivery details, including where and by when the goods or services are needed. And the payment terms you have agreed.

Spelling out the prices and quantities precisely is the point of the document. The PO is the agreed scope and cost made formal, so anything vague here becomes a dispute later.

Number your purchase orders

Like invoices, purchase orders should carry unique, sequential numbers. The PO number is the thread that ties the whole transaction together: it appears on the order, the supplier quotes it on their invoice, and your finance records match the two by it.

A clean numbering system, such as PO-001, PO-002, or a year-based format, keeps your orders organised and makes matching invoices straightforward. The same discipline that applies to invoice numbering applies here, and the approach in how to number your invoices carries over directly. Avoid gaps and never reuse a number, so every order can be referenced unambiguously.

Get it approved before you send it

The entire purpose of a purchase order is that the spend is authorised before it happens. So the approval step is not a formality to skip. Whoever in your business is responsible for signing off the spend should approve the PO before it goes to the supplier.

This protects both sides. For you, it means no order goes out without proper authorisation, which keeps spending under control. For the supplier, the approved PO is their assurance that the spend is committed and they will be paid, which is why they can start work on the strength of it. An unapproved or informal order gives neither party that protection.

How the PO connects to the invoice

The purchase order and the invoice are two ends of the same transaction. You write the PO to order and commit. The supplier delivers, then sends an invoice that quotes your PO number and matches the agreed amounts. Your finance process then checks that the invoice matches the PO before paying.

This matching is what makes the system work. When the invoice, the PO, and the record of what was delivered all agree, payment is fast and automatic. When they disagree, the invoice stops for investigation. So writing a clear, accurate PO up front directly determines how smoothly the eventual invoice gets paid. The full relationship is laid out in purchase order vs invoice, and the structure of the matching invoice is in what to put on an invoice.

Build one in minutes

A purchase order does not need special software. It needs the right fields, a unique number, and approval before it goes out. Lay out the buyer and supplier details, list the items with agreed prices, add the delivery and payment terms, and you have a document that authorises the spend and sets up a clean payment later.

You can produce one with the purchase order generator, which lays out the items, quantities, prices, and terms in a clean, numbered document, running in your browser with no signup and nothing stored on a server. Write it clearly, get it approved, and the order and the invoice that follows will line up without friction.

Common questions

What information goes on a purchase order?

A unique PO number, the date, your details as the buyer, the supplier's details, and a clear list of the items or services ordered, each with a description, quantity, and agreed unit price, plus line totals and an overall total. Add the delivery details, where and by when the goods or services are needed, and the agreed payment terms. Spelling out the prices and quantities precisely is the point of the document, since anything vague here becomes a dispute later.

Who creates the purchase order?

The buyer. The party committing to spend money raises the purchase order and sends it to the supplier, who then quotes its number on their invoice. So if you are the supplier doing the work, the client creates the PO. If you are buying from a supplier or a subcontractor, you create it for them. The direction never changes: the buyer orders, the seller invoices.

Why should a purchase order be approved before it is sent?

Because the whole purpose of a PO is that the spend is authorised before it happens, not questioned afterward. Whoever is responsible for signing off the spend should approve the PO before it goes to the supplier. This keeps your spending under control, and it gives the supplier the assurance that the spend is committed, which is why they can start work on the strength of an approved order. An informal, unapproved order gives neither side that protection.

How does a purchase order get matched to an invoice?

Through the PO number and the agreed figures. The supplier quotes your PO number on their invoice, and your finance process checks that the invoice matches the purchase order, and usually the record of what was delivered, before paying. When the order, the delivery, and the invoice all agree, payment clears automatically. When they disagree, the invoice stops for investigation, which is a common cause of delay. This is why writing a clear, accurate purchase order up front directly determines how smoothly the eventual invoice gets paid.

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Related articles

• What Is a Purchase Order and When Do You Actually Need One?
• Purchase Order vs Invoice: How They Work Together
• What to Put on an Invoice: The Complete Checklist