Why they happen
- The same invoice emailed to several people
- A vendor resending a statement or reminder
- Typos or prefixes added to an invoice number
- Manual entry on top of an automated feed
Signals worth checking
- Same vendor and invoice number
- Same vendor, amount and date with a different number
- Identical file contents under a different name
- Amounts that match an already paid bill
Making it routine
Run the check as invoices arrive, show the likely original next to the suspected duplicate, and let a person confirm. That keeps genuine repeat charges from being blocked.
Frequently asked questions
Can duplicate detection block legitimate repeat bills?
It should flag, not block. A person confirms, so a real recurring charge goes through.