Invoice Reconciliation in Construction: Match POs, GRNs & Invoices

Invoice reconciliation is where procurement control either holds or falls apart. If invoices are approved without checking them against purchase orders and delivery records, the business pays for things it did not order, did not receive, or did not agree to at that price. This guide explains how to run practical invoice reconciliation for UK construction teams.

What Invoice Reconciliation Means in Practice

Invoice reconciliation is the process of checking a supplier invoice against the purchase order (what was agreed) and the goods received note (what actually arrived). The goal is to confirm that quantity, price, and terms all match before the invoice is approved for payment.

• Compare invoice line items against PO line items (quantity, rate, description)
• Check invoiced quantities against GRN quantities (what was delivered and accepted)
• Verify VAT treatment, payment terms, and any agreed discounts
• Flag any discrepancies for review before approving payment
• Record the reconciliation result for audit purposes

Common Discrepancies in Construction Invoices

Construction invoicing is more complex than many industries. Part deliveries, call-off orders, price fluctuations, material substitutions, and variations all create legitimate reasons for invoices to differ from the original PO. The skill is distinguishing genuine discrepancies from acceptable variances.

• Short deliveries: invoice for full quantity but GRN shows partial receipt
• Price variances: invoice rate differs from the agreed PO rate
• Substitutions: different product supplied than what was ordered
• Duplicate invoices: same delivery invoiced twice under different references
• Unordered items: line items on the invoice that were never on a PO
• Incorrect VAT: wrong VAT rate applied, or CIS reverse charge not handled correctly

Handling CIS Reverse Charge on Supplier Invoices

Since March 2021, the CIS VAT reverse charge applies to most construction services between VAT-registered businesses in the CIS chain. This means the customer accounts for the VAT rather than the supplier. Invoices must be checked for correct reverse charge treatment to avoid VAT errors.

• Supplier invoices for construction services should show the reverse charge annotation
• The invoice should not charge VAT if the reverse charge applies
• The customer (you) must account for the output VAT on your own VAT return
• Materials-only supplies are generally outside the reverse charge
• End users and intermediary suppliers connected to end users are excluded
• Check each supplier's CIS and VAT status when setting up the purchase ledger

Dispute Resolution Workflows

When a discrepancy is found, the invoice should be held for investigation rather than approved or rejected outright. A clear dispute workflow prevents invoices from sitting in limbo and keeps supplier relationships intact.

• Put the invoice on hold with a clear reason code and description
• Notify the supplier of the discrepancy with supporting evidence (PO, GRN)
• Set a resolution target (e.g., 7 working days for the supplier to respond)
• Agree the corrected amount or accept a credit note for the difference
• Release the invoice for payment once the dispute is resolved
• Record the resolution for future reference and supplier performance tracking

Payment Term Management

Payment terms agreed at order stage should be honoured once the invoice is reconciled. Late payment damages supplier relationships and can trigger Late Payment of Commercial Debts Act interest. Early payment for a discount should be a deliberate decision, not an accident.

• Record agreed payment terms on every purchase order
• Calculate the payment due date from the invoice receipt date (not the invoice date)
• Batch payment runs to match agreed terms (e.g., 30-day, end-of-month)
• Track ageing of approved invoices to ensure terms are met
• Consider early payment discounts only where the cash benefit is clear
• Comply with the Prompt Payment Code if your organisation is a signatory