What is invoice processing, step by step?

What is invoice processing?

Invoice processing is the work accounts payable does on every supplier invoice: receive it, record its data, check that it is valid and not a duplicate, match it to the purchase order and the goods receipt, resolve any difference, get it approved, post it to the accounts and pay it on the due date.

It is the last part of procure-to-pay. By the time the invoice arrives, the purchase order has fixed the supplier, the price and the quantity, and the goods receipt has recorded what was delivered. Invoice processing checks that the supplier asks for what was agreed and delivered, and pays it once.

Take a simple case. A supplier emails a PDF invoice for 200 boxes of paper. Accounts payable finds the order and the delivery note from the PO number, sees that price and quantity agree, and schedules payment for the due date. Now a harder one: the invoice has no PO number, the amount is higher than the order, or the bank account is new. Each of these stops the invoice until someone decides. Good invoice processing makes the first case the normal one.

Vendor invoice management and “accounts payable invoice processing” are other names for the same work: managing supplier invoices from receipt to payment. Vendor invoice management is also a product name. OpenText sells Vendor Invoice Management for SAP Solutions, which it describes as automating document processing across procure-to-pay inside SAP. The steps and controls below are the same whatever the name.

Disclosure: the author works as an Ivalua consultant. The vendor product named on this page is described from its public documentation only.

What are the steps of invoice processing?

Invoice processing runs in eight steps. A small organisation may do several at once in its accounting package; a large one splits them between a shared service centre, buyers and budget holders.

1. Receive the invoice. Invoices arrive by e-invoicing network, supplier portal, email or post. One channel, or a short list of them, published to suppliers, avoids invoices lost in personal inboxes.
2. Capture the data. The invoice is registered with its supplier, number, date, amounts, tax and PO number. A structured e-invoice is read directly; a PDF or paper invoice is scanned and its data extracted by software or typed by hand.
3. Check validity and duplicates. The invoice must carry the content the law and the contract require, come from a known supplier record, and not repeat an invoice already registered (same supplier, number and amount, or near matches).
4. Match the documents. The invoice is compared with the purchase order and, for goods and many services, the goods receipt, line by line, within agreed tolerances. Invoices without a purchase order go to the approval route set for them instead.
5. Resolve exceptions. A difference in price, quantity or data stops the invoice. The buyer, the requester or the supplier fixes the cause: a corrected order, a missing receipt, or a credit note from the supplier.
6. Approve. A matched PO invoice is usually approved by the match itself. A non-PO invoice, or an exception outside tolerance, goes to the person with the authority to approve that amount.
7. Post and schedule payment. The invoice is posted to the general ledger. For PO invoices this clears the goods-received-not-invoiced balance created at receipt. The payment date is set from the payment terms.
8. Pay, reconcile and archive. The invoice is paid in a payment run to verified bank details, reconciled with the bank statement, and kept with its order, receipt and approvals for audit and tax.

How two-way, three-way and four-way matching work, and how to set tolerances, is the subject of a guide to three-way matching, in preparation.

What must a supplier invoice contain to be processed?

An invoice must be valid on its own before it is matched to anything. The minimum content is set by tax law and, for public buyers, by procurement law; the contract can add more, such as the PO number. An invoice that misses a required item can be returned to the supplier rather than corrected by the buyer. The table compares three common rule sets.

Public buyers must act quickly on invalid invoices. A US federal billing office must return an improper invoice within 7 days of receipt. A UK contracting authority that considers an invoice invalid or disputes it must tell the supplier without undue delay.

How are PO and non-PO invoices processed?

A PO invoice quotes a purchase order, so the system can match it and the approval already given for the order covers the payment. A non-PO invoice has no order behind it, so someone must approve it after the fact. The two routes need different rules.

PO invoice

Matched to the order and the receipt. If everything agrees within tolerance, no further approval is needed: the budget holder approved the spend when the requisition was approved. Only exceptions need a person.

Non-PO invoice

Routed to an approver by supplier, cost centre and amount, under the delegation of authority. Legitimate for categories the policy lists, such as rent, utilities, taxes or subscriptions. Outside them, a non-PO invoice usually means someone ordered without a purchase order.

Self-billing

The buyer issues the invoice itself from the goods receipt. EU VAT law allows it only with a prior agreement between the two parties and a procedure for the supplier to accept each invoice. Evaluated receipt settlement is a close practice: the buyer pays from the order and the receipt, with no supplier invoice.

Credit note

The supplier’s document that reduces or cancels an invoice, for example after a price error or a return. It is processed like an invoice and matched to the invoice it corrects.

The share of non-PO invoices tests the whole process. When it grows outside the listed categories, the fix is upstream: catalogues, contracts and purchase orders that requesters can use, and a “no PO, no pay” rule that sends such invoices back to the supplier for an order number, with written exceptions.

What are invoice exceptions, and how are they resolved?

An invoice exception is any invoice the process cannot pass without a person: the match fails, data is missing, or a check raises a doubt. Each exception has a typical cause and an owner. Resolving it fast matters, because the payment clock keeps running while the invoice waits.

The worked example below shows one invoice with three lines, checked against its order and receipt. The policy allows a price difference of up to 2% and no more than €50 per line; the contract gives free delivery on orders above €500. All data is fictional.

The arithmetic: 200 × €12.50 = €2,500 and 8 × €85 = €680, so €3,180 is due; €3,455 − €275 = €3,180. If the two missing cartridges arrive next week, the receipt is recorded and the supplier invoices them again. Without the checks, the organisation would have paid €275 more than it owed.

How fast must invoices be processed and paid?

Invoice processing has a deadline set by the payment terms, and in many places by law. Late payment costs interest, recovery costs and lost prompt-payment discounts. The table lists the main legal reference points.

Private companies outside these rules still need an internal deadline for each step: a fixed number of working days for each exception owner, written in the policy, then escalation to their manager.

How do you stop duplicate payments and invoice fraud?

Duplicate payments and fraud are stopped before the money leaves, because recovering it afterwards is slow and often fails. Three controls do most of the work.

• Duplicate checks on near matches. The same invoice often arrives twice, by email and by post, or with “INV-0412” on one copy and “412” on the other. Checks on supplier, date and amount catch what an exact match on the invoice number misses.
• Verified bank details. A change of bank account is confirmed by calling a known contact at the supplier, using a number already on file, never the one in the email asking for the change. Business email compromise, a fraud in which criminals pose as a supplier or an executive, led to reported losses of more than $3 billion in complaints filed with the FBI’s Internet Crime Complaint Center in 2025.
• Separation of duties. The person who creates or changes a supplier record does not approve that supplier’s invoices or release payments. Small teams that cannot separate these tasks add a review by someone else, as the US Government Accountability Office’s internal control standards allow.

All three rely on clean supplier data, which is part of supplier management; payment fraud through a supplier is covered in vendor risk management.

What changes with e-invoicing and automation?

An e-invoice in the strict sense is structured data that a system reads directly, not a PDF sent by email. A PDF must be read by software that extracts the data, and someone checks what it misread; a structured invoice arrives with every field in place, so the capture step disappears and the match can run at once.

Law is pushing structured invoices. EU public buyers must accept electronic invoices that follow the European standard EN 16931. Belgium has required structured invoices between VAT-registered businesses since 1 January 2026, and France began phasing in its mandate on 1 September 2026. The EU’s VAT in the Digital Age package allows every Member State to require e-invoicing. In India, GST-registered businesses with an aggregate turnover above ₹5 crore (since 1 August 2023) must report their invoices to other registered businesses on the government Invoice Registration Portal, which returns an invoice reference number. Whatever the format, EU VAT law requires the authenticity of origin, the integrity of the content and the legibility of an invoice to be ensured from the moment it is issued.

A vendor invoice management system, or invoice processing software, receives invoices from all channels, captures their data, runs validity and duplicate checks, matches them to orders and receipts, and routes exceptions and approvals with a record of each decision. It may be a module of the ERP, a dedicated accounts payable tool, or part of a procure-to-pay system. It cannot match an invoice to an order that was never raised. Guides to accounts payable automation and its software are in preparation.

How do you measure invoice processing?

Invoice processing is measured by how many invoices pass without a person, how fast the rest are resolved, and whether payments go out on time. Five indicators, counted the same way every month, are enough to start.