Duplicate payments in accounts payable: how they start, surface and get fixed

The most common failure in accounts payable is paying the same invoice twice. It usually starts when one bill reaches the system by more than one route and is keyed with slightly different details. It surfaces late and is fixed by recovering funds and tightening entry checks.

How it starts

A supplier emails an invoice to a buyer. The buyer forwards it to the payables inbox. Meanwhile the supplier, hearing nothing, sends a reminder copy to the same inbox. Or a paper original arrives after a scanned version was already processed.

None of this is unusual. Suppliers chase. Staff forward things to be helpful. The trouble begins at keying.

The first clerk enters the invoice number as printed. The second, working from a reminder, adds a suffix, drops a leading zero or types a slash as a hyphen. The system's duplicate check compares invoice number, supplier and amount. Because one field no longer matches exactly, the second entry passes as new.

Vendor master problems make it worse. If the same supplier exists under separate records, perhaps one created by purchasing and another by a clerk who could not find the first, the duplicate check never compares the two bills at all. Each record looks clean on its own.

Purchase order matching does not always save the day either. Invoices without an order, such as utilities, rent or professional fees, skip the match entirely. Where an order exists but was received in partial quantities, a second bill can consume the remaining open balance and look perfectly valid.

Why the controls miss it

Approvers see one invoice at a time. They confirm the goods or service was received and that the cost centre is right. They are not shown the earlier payment, so they approve in good faith.

Payment runs are reviewed by total and by unusual payees. A repeat bill from a regular supplier for a normal amount does not stand out. It travels through the run with everything else.

Accruals add a quieter layer of confusion. If month end booked an accrual for the expected bill and the reversal posted against only one of the two entries, the ledger can look roughly right while cash has gone out twice.

How it gets spotted

Most often the supplier's credit control team notices first. They find an unapplied amount on their side and either call to ask what it covers or simply hold it as credit. Many never call. The overpayment sits on their ledger until a statement reconciliation turns it up.

Other signals appear inside the business. A budget holder queries an expense line that seems high. A supplier statement shows a credit balance where payables shows nothing owed. Bank reconciliation is less help here, since both payments cleared and both were recorded.

Year end can expose it too. When annual payment reports to tax authorities are prepared, a supplier whose reported total looks inflated against what they billed is worth a closer look.

The most reliable detection is deliberate. A periodic scan of paid invoices using fuzzy matching on number, near amounts and close dates across all supplier records will catch what the entry check let through.

How it is fixed

First, confirm it is a true duplicate and not a second legitimate delivery. Pull both documents, the order and the receipt. Ask the budget holder whether one or two deliveries happened.

Then recover the money. Asking for a refund is cleaner than taking a credit against future bills, because a credit can be forgotten or applied wrongly. Where the supplier relationship is ongoing, an offset may be the practical choice, but it should be recorded as a specific credit note linked to the original invoice.

The accounting correction follows. Reverse the expense on the duplicate, set up a receivable from the supplier and clear it when funds return. If an accrual reversal was misapplied, fix that in the same period. Corrections made after close need a journal with clear support, since auditors will ask.

Finally, close the gap that let it happen. Typical repairs include normalising invoice numbers before the duplicate check runs, merging duplicate supplier records and blocking new ones that share a tax identifier or bank account with an existing record. A single intake channel for invoices removes most of the problem at the source.

Questions to ask the people who run it

• How do invoices actually arrive, and how many inboxes or desks receive them before payables does?
• When a supplier sends a reminder, what happens to it?
• Does anyone ever override the duplicate warning? Under what circumstances, and is the reason recorded?
• Who can create a supplier record, and what do they check before creating one?
• How are invoice numbers typed when they contain letters, spaces or symbols?
• Which invoices are paid without a purchase order, and who confirms receipt for those?
• When a supplier reports an overpayment, who handles it and where is it logged?
• Are supplier statements reconciled, and for which suppliers?
• After a duplicate is found, does anyone trace why it happened, or is it just reversed?

The answers often reveal workarounds that never made it into the procedure manual. A clerk who adds a suffix to avoid a system warning, or a buyer who keys invoices directly to save time, explains more about this failure than any process map.

APQC's Process Classification Framework® (PCF) is an open standard developed by APQC, a nonprofit that promotes benchmarking and best practices worldwide. To download the full PCF or to view definitions and measures, please visit www.apqc.org/pcf.