PO vs Non-PO Invoice: Difference, Examples, Processing

The difference between a PO invoice and a non-PO invoice is simple: a PO invoice references a purchase order number and was pre-approved through procurement before the order was placed, while a non-PO invoice arrives with no purchase order attached because the spend happened outside the normal purchasing process. That one distinction changes how your accounts payable team handles the bill, who has to approve it, how much risk it carries, and how long it takes to pay.

Most accounts payable departments process a mix of both, and the ratio matters. PO invoices flow through almost on their own once the numbers line up. Non-PO invoices need a human to code them, find an approver, and confirm the company actually agreed to the charge. This guide explains what each type is, the key differences side by side, real examples of both, how AP processes them, why non-PO invoices carry more risk, and how to bring more of your spend under purchase orders.

What is a PO invoice?

A PO invoice is a supplier bill that references a purchase order number issued before the goods or services were ordered. Because the buyer, the item, the quantity, and the price were all approved during the requisition and PO step, the invoice is effectively pre-approved. The accounts payable team's job is to confirm the invoice matches the purchase order and the receiving record, not to re-litigate whether the purchase should have happened.

That up-front approval is the whole point of a purchase order. Procurement agrees to the spend, encodes it in a PO, and sends the PO to the supplier. When the invoice arrives quoting that PO number, AP runs a three way match across the invoice, the purchase order, and the goods receipt. If the three documents agree within tolerance, the invoice can move to payment with little or no manual review.

What is a non-PO invoice?

A non-PO invoice is a supplier bill that has no purchase order behind it. The spend happened outside the formal purchasing process, so there is no PO to match against and no prior approval on file. When a non-PO invoice lands, the accounts payable team has to figure out three things from scratch: which general ledger account it belongs to, whether the charge is legitimate, and who in the business has the authority to approve it.

Non-PO invoices are common and often unavoidable. They cover the small, recurring, or unplanned costs that do not justify raising a purchase order, plus contracted services billed on a schedule. The tradeoff is control. Without a PO setting the price and scope in advance, every non-PO invoice depends on someone after the fact confirming the company agreed to pay it.

PO vs non-PO invoice: the key differences

The two invoice types differ across approval, matching, risk, and speed. This table summarizes where they part ways.

Factor	PO invoice	Non-PO invoice
Purchase order	Yes, references a PO number	No PO attached
Approval timing	Pre-approved during requisition	Approved after the invoice arrives
Matching	Two or three way match to PO and receipt	No PO to match; manual review
GL coding	Inherited from the PO	Assigned by AP per invoice
Processing speed	Faster, often touchless	Slower, manual routing
Risk of error or fraud	Lower, controls are up front	Higher, no spend limit set in advance
Typical use	Planned, larger, direct purchases	Small, recurring, or unplanned spend

The headline is that a PO invoice carries its controls up front, while a non-PO invoice pushes all of that work to the back end. PO invoices are generally more transparent, less prone to error, and faster to clear. Non-PO invoices take more time because AP has to build the approval trail after the fact.

Examples of PO and non-PO invoices

PO invoices usually cover planned, direct purchases where the company knew what it was buying ahead of time:

Raw materials or inventory ordered from a supplier against a signed PO
A bulk order of laptops for a new hiring class
Contract manufacturing runs with agreed unit pricing
Capital equipment approved through procurement

Non-PO invoices tend to be smaller, recurring, or one-off costs that arise as the need comes up:

Monthly utilities, internet, and phone bills
Employee expense reimbursements and travel costs, often backed by receipts rather than a PO. If your team still keys those by hand, a receipt data extraction tool pulls the line items off each receipt before they ever reach AP.
Legal, accounting, or consulting fees billed on a contract
Subscriptions, software renewals, and membership dues
Office supplies and small ad-hoc purchases

A useful rule of thumb: if procurement issued a purchase order before the spend, it is a PO invoice; if the charge showed up first and someone has to approve it afterward, it is a non-PO invoice.

How are PO invoices processed?

PO invoices follow a matching path. When the invoice arrives, the accounts payable system captures the header and line data, finds the referenced purchase order, and compares the two. In a two way match it checks the invoice against the PO. In a three way match it adds the goods receipt so it confirms the items were actually delivered before paying. As long as quantities, prices, and totals agree within a set tolerance, the invoice posts and moves to payment without anyone re-approving the spend.

Because the approval already happened at the PO stage, a clean PO invoice can be fully touchless. The exceptions are mismatches: a price that drifted, a short shipment, or a quantity that does not tie out. Those route to a buyer or AP clerk to resolve. Automating this matching is exactly what invoice matching software does, and it is where most of the time savings in AP come from.

How are non-PO invoices processed?

Non-PO invoices take a different path because there is nothing to match against. The accounts payable team has to code each invoice to the right general ledger account and cost center, then route it to whoever has the authority to approve that spend. Approval is determined by the company's authorization rules, usually based on the amount and the department or budget owner. Only after an approver signs off does the invoice move to payment.

This is more work and more judgment. AP has to know who owns the budget, apply the correct codes, and chase down approvers who may not be expecting the bill. Good invoice approval software automates the routing: it reads the invoice, suggests the GL coding, and sends it to the right approver based on rules you set, with a full audit trail of who approved what and when. That is the difference between a non-PO invoice sitting in someone's inbox for two weeks and clearing in a day.

Why are non-PO invoices riskier?

Non-PO invoices are riskier because no spend limit, price, or scope was agreed before the money was committed. With a PO invoice, procurement set the terms in advance and the match enforces them. With a non-PO invoice, the company is reacting to a bill that already exists, so the controls that catch overcharges, duplicate payments, and fraudulent invoices have to work after the fact instead of before.

A few specific risks show up more often with non-PO spend. Duplicate payments are easier to miss because there is no PO to anchor the invoice to. Maverick spend, where employees buy outside policy, lands entirely as non-PO invoices. And fake or inflated invoices have a better chance of slipping through when nobody pre-approved the amount. Strong coding rules, approval thresholds, and a consistent invoice approval process are what keep non-PO spend under control.

How to reduce non-PO invoices

You will never get non-PO invoices to zero, and you should not try. Utilities, employee reimbursements, and some contracted services rarely justify a purchase order. The goal is to move the spend that should be on a PO onto one, so more of your invoices flow through matching instead of manual approval. A few practical steps:

Set a PO threshold. Require a purchase order for any planned spend above a dollar amount, so large purchases always carry up-front approval.
Make requisitioning easy. If raising a PO is painful, people skip it. A simple intake form removes the excuse.
Track your PO coverage rate. Measure the share of invoices that reference a PO and aim to raise it over time. It is one of the more telling accounts payable process metrics.
Educate budget owners. The people who commit spend need to know when a PO is required and why it protects them.

Even with a strong PO program, you still need a clean way to handle the non-PO invoices that remain. That is where automation earns its keep on both sides.

How automation handles both PO and non-PO invoices

Modern accounts payable automation captures every invoice the same way, then sends it down the right path. PO invoices get matched to the purchase order and receipt automatically, clearing without a human touch when everything ties out. Non-PO invoices get coded with suggested GL accounts and routed to the correct approver based on your rules. Both paths flag duplicates and exceptions, and both write a complete audit trail back to your accounting system.

The result is that your team spends its time on the genuine exceptions, the price mismatch or the missing approver, rather than keying data and forwarding emails. Accounts payable software that handles PO and non-PO invoices in one workflow is how AP teams move toward touchless invoice processing without losing control over the spend that never had a purchase order. Once the data is captured, you can also export clean line-item detail to extract invoice data to Excel for analysis or audit.

If you are comparing options, our guide to the best AP automation software walks through what to look for in capture accuracy, matching, and approval routing.

Frequently asked questions

What is the difference between a PO and a non-PO invoice?

A PO invoice references a purchase order number and was pre-approved through procurement before the order was placed. A non-PO invoice has no purchase order attached, so accounts payable has to code it and route it for approval after the invoice arrives. The PO invoice is faster and lower risk because its controls are set up front.

What is an example of a non-PO invoice?

Common non-PO invoices include monthly utility and internet bills, employee expense reimbursements, legal and consulting fees, software subscriptions, and small office supply purchases. These are costs that arise as needed without a purchase order, so they are approved after the bill arrives rather than before the spend was committed.

How are non-PO invoices processed in accounts payable?

Non-PO invoices are coded to the correct general ledger account and cost center, then routed to an approver based on the company's authorization rules, usually by amount and department. Because there is no purchase order to match against, a person has to confirm the charge is valid before it moves to payment, which makes the process slower than for PO invoices.

Why are non-PO invoices riskier than PO invoices?

Non-PO invoices are riskier because no price, scope, or spend limit was agreed before the money was committed. The controls that catch overcharges, duplicate payments, and fraudulent invoices have to work after the fact rather than at the purchase order stage, so maverick spend and errors are easier to miss without strong coding and approval rules.

Can a non-PO invoice be converted to a PO invoice?

Not retroactively in a meaningful sense. Once spend has happened without a purchase order, the invoice is a non-PO invoice. You can raise a PO after the fact for the audit trail, but the up-front approval that defines a PO invoice did not occur. The better fix is requiring a purchase order before similar spend happens next time.

What percentage of invoices should be PO invoices?

There is no universal number, but most AP teams aim to put as much planned, larger spend on purchase orders as practical while accepting that utilities, reimbursements, and some services stay non-PO. Tracking your PO coverage rate and raising it over time pushes more invoices into automated matching and reduces the manual approval workload.