A purchase order is a document a buyer issues to a supplier committing to buy specified goods or services at an agreed price, quantity and set of terms. Once the supplier accepts it, it becomes the commercial basis for delivery, the invoice and payment. It is also the reference point that later checks, such as invoice matching, compare against.
Why does a purchase order matter once agents act?
A purchase order is a commitment of the business's money made before any invoice exists. That puts it earlier in the chain than most finance controls, and makes it a natural place to check that spending was approved. If an agent raises purchase orders, it is entering into obligations on the business's behalf, which is a different kind of act from coding an invoice that already exists.
Purchase orders also make agents better downstream. An invoice with a matching order can be checked line by line for price and quantity. An invoice without one has to be investigated. That is why AI agents for finance work best where purchase orders are used consistently.
What does a purchase order contain?
- A unique PO number, which the supplier must quote on the invoice.
- Supplier name and the supplier's identifier in the master file.
- Items or services, quantities, unit prices and total value.
- Delivery address and date, or the service period.
- Payment terms and any contract reference.
- The cost centre or budget it is charged to.
- The approver, recorded against the value approved.
How does an agent work with purchase orders in practice?
There are three distinct jobs, with different depths. Drafting a purchase order from an approved requisition is depth 2 or, once certified for routine items within a value limit, depth 3. Approving a purchase order is a spending decision that belongs to the budget holder, which is why can an AI agent approve purchase orders? is usually answered with conditions. Matching invoices to orders is routine checking an agent can do at volume.
Whether the agent may issue the order to the supplier directly is covered in can an AI agent raise a purchase order?
What does that look like in an example?
A hospital trust's facilities team submits a requisition for 200 boxes of cleaning supplies from the contracted supplier. The agent checks the item against the contract price list, confirms the budget has room, and drafts a purchase order for 1,400. The value is under the limit set for routine consumables from contracted suppliers, so the order is issued and recorded. A second requisition, for a new floor-cleaning machine at 9,000 from a supplier with no contract, is drafted and held for the budget holder.
How is a purchase order different from a purchase requisition?
A requisition is an internal request: someone in the business asks to buy something. A purchase order is the external commitment that follows once the request is approved. The requisition stays inside the organisation; the purchase order goes to the supplier and binds the business. Agents often handle both, and the controls should step up between them, as described in how to process purchase requisitions with an AI agent.
Which related terms should you know?
- Purchase-to-pay: the whole process from need to payment, of which the purchase order is one step.
- Three-way match: checking an invoice against the order and the goods receipt.
- Non-PO invoice: an invoice with no order behind it, covered in how to handle invoices that arrive without a purchase order with an AI agent.
Questions people ask
Is a purchase order legally binding?
Once the supplier accepts it, a purchase order usually forms or evidences a contract, though the effect depends on its terms and the governing law. That is the reason an agent issuing orders should be bounded by value, supplier and category: it is committing the business, not just recording.
Do all purchases need a purchase order?
No. Most businesses exempt categories such as utilities, rent and small expenses, and use other controls for them. The policy should be written down so an agent can tell a legitimate non-PO invoice from one that skipped the process.