Duplicate invoice: vendor plus number, nothing else
A duplicate is the same vendor and the same invoice number arriving twice. File names and dates are unreliable keys — vendor and number are not.
5 documents free. PDF, photo or XML — data out as CSV, Excel or JSON.
Why it happens
The same invoice arrives by email and through a portal. Two files, one invoice.
A supplier resends after a resend request, and both copies get processed.
How to detect it
Key on vendor identity (tax ID or vendor record) plus invoice number.
Flag, do not auto-delete: sometimes two invoices legitimately share a number across different entities.
What it costs
Paying twice is recoverable but slow: credit note, follow-up, reconciliation.
At volume, a few duplicates a quarter is normal — and invisible without a check.
Where the check belongs
At intake, before approval — not at payment, when it is already too late.
Frequently asked
Can the same invoice number be legitimate twice?
Across different vendors yes; within one vendor it is an error worth querying.
Does extraction catch duplicates automatically?
It can flag them at intake, which is the cheapest moment to stop them.