What is three-way matching?

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Three-way matching is the process of verifying a supplier invoice against two other documents — the original purchase order (PO) and the goods receipt note (GRN) — before approving payment. All three documents must agree on quantity, price, and supplier before an invoice is cleared for payment.

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It is the standard control mechanism in Procure-to-Pay (P2P) and the primary defence against duplicate payments, overbilling, and fraudulent invoices.

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Why three-way matching matters

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Without a matching process, businesses are exposed to paying invoices that do not correspond to actual purchases, paying more than was agreed, or paying the same invoice twice. Three-way matching closes these gaps by requiring that payment is only authorised when the business can confirm it ordered the goods (PO), received the goods (GRN), and the invoice matches both.

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For high-volume AP environments — retailers, manufacturers, large enterprises — this control also scales the validation process, allowing matching to happen systematically rather than through manual review of every invoice.

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How three-way matching works

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Step 1 — Purchase order. A buyer raises a PO specifying supplier, item, quantity, and agreed price. The PO is approved internally before being sent to the supplier.

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Step 2 — Goods receipt. When the goods or services are delivered, a goods receipt note is created confirming what was actually received — quantity, condition, date.

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Step 3 — Supplier invoice. The supplier issues an invoice for the goods delivered, referencing the PO number.

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Step 4 — Matching. The AP system compares all three documents. If supplier, quantity, and price agree within defined tolerances, the invoice is automatically approved for payment. If any field falls outside tolerance, the invoice is flagged as an exception for manual review.

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Two-way matching vs three-way matching

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Two-way matching compares only the invoice against the PO — without requiring a goods receipt. It is simpler and faster, but provides less assurance that goods were actually received. Three-way matching adds the goods receipt step, making it the stronger control for physical goods. For services, where a GRN is not always practical, two-way matching is more common.

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Where matching breaks down

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The most common exceptions in three-way matching are: price variances (invoice price differs from PO price), quantity variances (invoice quantity differs from GRN quantity), and missing PO references on supplier invoices. Each requires manual investigation, which is where AP teams spend most of their time.