How to catch duplicate invoices across blocks

To catch duplicate invoices across blocks, compare each new invoice with everything already posted for that supplier on every block and schedule you manage, matching on supplier, invoice number, invoice date, amount and the work or period described. An exact match on supplier and invoice number is a duplicate, and the same amount and work under a different number or on a different block is a likely duplicate to query with the contractor before anything is paid.

This guide covers how duplicates get onto two blocks, which fields to compare, how strict to make the match, and what to do when you find one.

How does one invoice end up on two blocks?

• A contractor works across an estate and sends the same invoice to two property managers, who each code it to their own block.

• An invoice is coded once to a block schedule and once to the estate schedule, because the work served both.

• An invoice addressed to the RMC with the estate name and no block is coded to one block, then sent again with the right block named.

• A copy is resent by email after the original came by post, or attached to a statement or a reminder.

• An invoice is reissued with a new number after a correction, and the original is never credited.

• A quote or pro forma is processed, and then the final invoice for the same work.

Any of these can happen without anyone meaning it to. Each one takes money from the wrong fund until someone notices.

Which fields should you compare?

• Supplier: match on the VAT number and bank details as well as the name, because the same contractor can appear under a trading name and a company name.

• Invoice number: compare it after removing spaces, prefixes and leading zeros, so that a number typed slightly differently still matches.

• Invoice date, and for utilities and contracts, the period the invoice covers.

• Amounts: the net, the VAT and the total.

• The work: the description, the site address, and any job number or purchase order reference.

Gov.uk guidance says an invoice must include a unique identification number. So two invoices from one supplier with the same number should be the same invoice, whichever block they were coded to.

How strict should the match be?

Treat matches in three tiers:

Exact match

Same supplier and the same invoice number, after cleaning up the number. Stop the second invoice. It is a duplicate unless the contractor confirms otherwise in writing.

Strong match

Same supplier and the same total, with invoice dates close together, on a different block or schedule. Hold it and ask the property managers for both blocks, and if needed the contractor, which block the work was for.

Weak match

Same supplier and the same job number or description, with a different invoice number and amount. This can be a reissue, a stage payment or a separate visit. Look at both invoices side by side before approving.

Watch for genuine repeats. A monthly cleaning contract bills the same amount every month, so the service period is what tells one month from the next. Leave the period out of the comparison and every month looks like a duplicate.

Why does the check have to cover every block?

A duplicate check that only looks within one block misses the case this guide is about: the same invoice posted once to each of two blocks. Each block’s ledger looks clean on its own. The duplicate only shows when the check runs across every block that supplier works on.

The same applies to schedules within one block. A cost on the block schedule and the same cost on the estate schedule are both inside one property, and both are paid by leaseholders.

Why do duplicates matter to leaseholders?

Under section 19 of the Landlord and Tenant Act 1985, costs count towards a service charge only to the extent they are reasonably incurred. A duplicate is a cost nobody incurred. If it sits on the wrong block, one block’s leaseholders pay for work done at another. If it sits on both, the contractor is paid twice from service charge funds.

In England, the RICS Service Charge Residential Management Code (4th edition, March 2026, section 5.11) says that approving the service charge accounts confirms they represent the actual expenditure incurred. A duplicate found after the accounts are approved has to be put right in a later year, and explained.

What should you do when you find one?

1. Hold the invoice that arrived second, on every block it was coded to.

2. Find out which block, and which schedule, the work was for. The property manager usually knows.

3. If both copies were paid, ask the contractor for a refund or a credit note against the duplicate.

4. Where an invoice was reissued, match the credit note for the original to the new invoice.

5. Correct the coding, and record what happened and who confirmed it.

A supplier statement is the backstop. It shows each invoice once, in the supplier’s own numbering, so a duplicate posted to two blocks stands out when the two are compared. See supplier statement reconciliation for block management.

Our guide to handling a supplier bank detail change sets out that call step by step.

Where Dataforge Invoices fits

Dataforge Invoices is AP software for UK block and estate managing agents. Duplicates, bank detail mismatches, new suppliers, purchase orders and posting limits are checked before anything is posted. Identical files are caught at intake, and potential duplicate invoices are flagged within your duplicate window. Anything uncertain goes to one review queue, with the reason named.

These checks support your existing controls. They do not on their own prove that a supplier or an invoice is genuine, and deciding which block the work was for stays with your team.

Sources: Landlord and Tenant Act 1985, section 19; RICS Service Charge Residential Management Code, 4th edition section 5.11; GOV.UK, invoices: what they must include. Checked 16 October 2026.