What Is Purchase Order?
A buyer’s authorized request specifying items, quantities, and prices.
Detailed Explanation
Creates commitment before invoice. Matching PO to invoice prevents overpayment.
Example
Procurement issues PO #4421 for fifty licenses at agreed rates.
Why It Matters
Control spend and speed three-way match.
Key facts
- A purchase order (PO) is a buyer-issued document authorizing a vendor to deliver specific goods/services at agreed prices and terms — it becomes a legally binding contract once accepted.
- Standard PO fields: PO number (unique), buyer and vendor details, description of items, quantities, unit prices, total, delivery date, ship-to address, payment terms, and authorized buyer signature.
- POs are central to three-way matching: PO → Receipt → Invoice. All three must agree before payment is approved.
- B2B transactions over a few thousand dollars typically require POs in established companies; smaller transactions often use simplified credit-card or autopay arrangements.
- Modern e-procurement systems generate POs automatically when requisitions are approved, reducing manual processing time by 60-80%.
How it shows up in practice
A 200-person manufacturing company's procurement system generates PO #2026-04482 to a parts supplier for 500 brackets at $14.20 each ($7,100 total) with a delivery date of April 30 and net-30 payment terms. When the supplier's invoice arrives in May referencing PO 2026-04482, AP runs three-way matching: invoice line items match PO, quantities match the goods receipt note, and payment is auto-approved. Without the PO reference, the invoice would route to manual review.
Common mistakes
- Issuing POs verbally or by email without proper PO numbers — defeats the purpose of formal procurement controls.
- Failing to update PO totals when scope changes — creates invoice disputes when actual delivery exceeds PO amount.
- Not training receivers on goods receipt notes (GRNs) — breaks three-way matching and slows AP.
- Allowing 'after-the-fact POs' (creating a PO after the work was done) — undermines budget control and approval discipline.
- Using sequential PO numbers that customers can guess (e.g., PO #1, #2) — minor security/competitive intelligence concern.
Frequently asked questions
Is a purchase order a contract?
Yes, once accepted by the vendor. The PO contains offer (buyer) and the vendor's acceptance (often by acknowledgment or shipping the goods) creates a binding contract. Some companies use a separate Master Service Agreement (MSA) plus POs that reference it.
What's the difference between a purchase order and an invoice?
Purchase order: buyer-issued, BEFORE delivery, authorizes the vendor to fulfill. Invoice: vendor-issued, AFTER delivery, requests payment. Both should reference the same PO number for matching.
Do small businesses need to issue POs?
Not legally required, but useful once you spend more than ~$1,000 per transaction or have multiple approvers. POs create paper trails for budget control, authorization, and audit. For tiny businesses, credit-card receipts may suffice.
What's a blanket PO?
A blanket PO (or BPO) authorizes recurring purchases over a defined period (often 6-12 months) at agreed prices, with releases against the blanket for individual orders. Common for office supplies, IT consumables, and ongoing professional services.
Can I cancel a PO after it's issued?
Generally yes if not yet accepted by the vendor — you can withdraw the offer. After acceptance, cancellation requires vendor agreement and may incur cancellation fees. Most POs include cancellation terms in the standard purchasing terms and conditions.
Related Resources
Last verified: May 2026
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