Duplicate payments rarely announce themselves. They sit in paid history until someone goes looking.
Export 12 to 24 months of paid invoices with supplier, reference, date, amount and payment details. Normalise references and supplier names, then run exact, near-match and cross-supplier tests. Confirm each candidate against source documents and the supplier's statement before asking for money back, and fix the cause so it doesn't happen again.
Decide the period, usually 12 to 24 months, and which entities and currencies are included. Use paid invoices, but keep credit notes in a separate list, because they explain many apparent duplicates.
For each paid invoice you need: supplier ID and name, supplier bank account, invoice reference, invoice date, gross amount, currency, purchase order number, payment date and payment reference. The bank account matters: it's how you find the same payee set up twice.
The Excel formulas for these tests are set out step by step.
Sort each candidate into confirmed, possible or false positive. Pull the source documents for anything confirmed or possible: both invoices, both payments, and the purchase order. Legitimate repeats, such as monthly service charges, drop out here.
Before contacting the supplier, request their statement. Overpayments often show up there as unallocated cash or a credit balance in your favour, which makes recovery straightforward. See supplier statement reconciliation.
Write to the supplier with both invoice references, both payment dates and amounts, and ask for a refund or a credit note against future invoices. Keep the tone factual; most suppliers return duplicates promptly when the evidence is clear. Some firms specialise in recovery audits for a share of what they recover; for most teams the steps above are enough.
For each confirmed duplicate, record why it happened: a re-keyed invoice, a duplicate supplier record, a statement chase that re-entered a paid invoice. Fix the control, not just the transaction. Report the count, the value found, the value recovered and the fixes made.
Paste your invoice list and see likely duplicates in minutes. Free Excel file: enter your work email to download it.
The Accounts Payable Control System runs four duplicate-invoice tests, supplier master fraud checks and a three-way match on every invoice, with a payment run release gate that blocks release while exceptions are open. Excel, no macros, one-time price.
Most teams use 12 to 24 months. Further back, documents are harder to find and suppliers are less able to process refunds.
It varies widely with volumes, systems and controls. The useful measure is your own trend: count and value found per audit, falling over time as controls improve.
No. Confirm with your own documents and the supplier statement first. Then contact them with the specific invoices and payments.
Yes. For most mid-sized companies, a year of paid invoices fits comfortably in Excel. The tests are COUNTIFS and SUMPRODUCT formulas on normalised references, amounts and dates, so no specialist software is needed to find the candidates.
Last updated 18 October 2026. General guidance for finance teams; check it against your own policies, systems and local rules.