What Is a Purchase Order and Why Does Your Business Need One?

What Is a Purchase Order?

A purchase order (PO) is a formal document issued by a buyer to a seller that authorises a specific purchase. It describes exactly what is being purchased, in what quantity, at what agreed price, and under what delivery and payment terms.

Unlike an invoice — which flows from seller to buyer as a payment request — a purchase order flows from buyer to seller. It is the buyer saying: "We formally authorise this purchase. Here is our reference number. Please proceed." Once the seller accepts the PO, it becomes a legally binding contract between both parties.

Why Small Businesses Skip POs — and Why That Is a Mistake

Small businesses typically operate informally. A supplier is found, a price is agreed by phone or email, goods are ordered, and an invoice arrives later. The PO step is skipped entirely.

This works fine — until it doesn't. Without a PO, there is no written record of what was ordered, at what price, and by whom. When the invoice arrives with a different price, a different quantity, or an item that was not ordered, there is nothing to reference. The dispute becomes a "he said / she said" conversation, and resolution is slow, painful, and relationship-damaging.

5 Reasons to Use Purchase Orders

1. Budget Control

A PO must be approved before a purchase is made. This single requirement ensures that someone with budget authority signs off on every significant spend. Without POs, employees can commit the business to expenses that haven't been budgeted — a common cause of cash flow surprises in growing businesses.

2. Dispute Prevention

A PO establishes a clear written record of what was ordered — quantities, specifications, unit prices, and delivery terms. When the supplier's invoice arrives, it can be checked against the PO. Any discrepancy is immediately visible and can be queried before payment is made, rather than after.

3. Audit Trail

Accountants, auditors, and tax authorities love purchase orders because they create a clean chain of documentation from authorisation to receipt to payment. During a tax audit or financial review, being able to match every payment to an approved PO and a goods receipt is a significant advantage. Businesses without POs struggle to prove that payments were legitimate business expenses.

4. Supplier Confirmation

A PO gives the supplier a formal document to work from. They know exactly what is expected — quantities, specifications, delivery address, and required date. This reduces errors and eliminates ambiguity that leads to wrong goods being shipped or services being delivered at the wrong time.

5. Three-Way Matching

The gold standard of accounts payable is three-way matching: comparing the purchase order, the goods receipt (or delivery note), and the supplier invoice. Payment is only approved when all three documents agree. This process, standard in large organisations, virtually eliminates fraudulent or erroneous payments. Small businesses that adopt even a simplified version of three-way matching dramatically reduce payment errors.

What a Purchase Order Should Include

• Unique PO number (for tracking and reference)
• Date of issue
• Buyer's name, address, and contact details
• Supplier's name, address, and contact details
• Itemised list of goods or services with quantities and agreed unit prices
• Total order value and currency
• Required delivery date and address
• Payment terms (e.g. net 30 days from invoice date)
• Any special terms or conditions
• Authorised signature or approval

PO Numbering and Tracking

PO numbers should follow a consistent, sequential format — for example, PO-2024-001, PO-2024-002, and so on. The year prefix makes it easy to identify when a PO was issued. When a supplier invoice arrives, it should always quote the PO number. This is what allows the three-way match to work and enables accounts payable teams to process invoices without delays.

Always instruct your suppliers to include your PO number on their invoices. Many corporate buyers will return an invoice unpaid if it does not carry a valid PO reference.

Generate Your First Purchase Order Free

GoWin Tools' purchase order generator creates professional, numbered POs in your browser — no account, no subscription, completely free. Download as PDF and send to your supplier in seconds.

Create a free purchase order →