Three-Way Matching in Construction: PO vs GRN vs Invoice
Learn how three-way matching works in construction procurement. Compare purchase orders, goods received notes, and supplier invoices before payment is approved.
Overview
Three-way matching means checking three records before you authorise payment: the purchase order, the goods received note, and the supplier invoice. In construction, that is often the difference between controlled spend and margin leakage hidden inside accounts.
The three documents you are checking
Each document answers a different question. The purchase order says what you agreed to buy. The GRN says what arrived. The supplier invoice says what the supplier wants to be paid for. The job of three-way matching is to make sure those three stories line up.
- PO: what was ordered, approved, and committed
- GRN: what was delivered and accepted
- Invoice: what the supplier is requesting payment for
What variances should be flagged?
A good matching process does not just check totals. It checks quantities, rates, VAT treatment, and whether the invoice references the right order and delivery record.
- Invoice quantity exceeds goods received
- Invoice rate does not match the approved PO
- Duplicate invoice submitted against the same order
- Invoice raised before any delivery has been confirmed
- Unexpected VAT treatment or line items
Why this matters in construction
Construction procurement is messy by default. Part deliveries, call-offs, supplier substitutions, and site changes all create room for invoicing errors. Three-way matching gives commercial and finance teams a disciplined check before money leaves the business.
- Protects margin on repeat material and plant orders
- Reduces arguments between site, commercial, and accounts
- Improves audit trail for approvals and disputes
- Stops payment on incomplete or inaccurate invoices
How to keep matching practical
The process has to be tight enough to catch real variances but simple enough that teams will actually use it. The best setup automates routine matches and only surfaces the exceptions that need review.
- Keep supplier, PO, and item records clean
- Capture GRNs consistently on site
- Auto-match exact or near-exact cases
- Send exceptions for review before payment approval
- Feed approved invoices into accounting after checks pass
Key Takeaways
- Three-way matching checks order, delivery, and invoice before payment
- It is most valuable where part deliveries and supplier variance are common
- The goal is not bureaucracy. It is catching exceptions before they hit margin
- POs and GRNs become much more valuable when they are part of the invoice workflow