How to check duplicate invoices before payment

Duplicate invoice checks should happen before money moves. Once a duplicate reimbursement or vendor payment enters the books, the cleanup takes longer than the original review.

Compare more than amount

• Invoice number
• Supplier or merchant
• Date
• Currency
• Amount
• File fingerprint when available
• Normalized OCR fingerprint

Amount alone is a weak signal. Two meals can cost the same. Two SaaS subscriptions can bill the same monthly amount. The strongest matches combine invoice number, merchant, date, and currency.

Keep the duplicate row

Do not delete the repeated row immediately. Mark it as duplicate, keep the original visible, and exclude the duplicate from clean export. This gives the team a record of the decision.

Watch recurring invoices

Recurring vendors create a special case. They may share the same merchant and amount every month, but the invoice number and date should change. A reviewer should treat repeated invoice numbers as higher risk than repeated amounts.