Look for a duplicate candidate
The strongest starting point for a two-document check is the same supplier and invoice number. This can indicate an emailed reminder, a resent PDF, a revised copy, or an invoice that was already entered. It does not tell you which of those explanations is correct.
Use consistent supplier names when comparing. A trading name, abbreviation, and legal name may refer to the same business, but a tool should not silently assume that connection.
Compare the complete context
Check the amount, currency, invoice date, service period, purchase order, and any credit note. Two invoices for the same amount might be ordinary monthly rent or a recurring retainer. Different totals may indicate a revision rather than two separately payable invoices.
If a supplier reused an invoice number, ask which document supersedes the other and retain that clarification. Keep both originals if your normal recordkeeping process requires them.
Check the ledger and actual payment record
Once you identify a candidate, search your accounting records for the original entry, its status, and any linked payment. Also check whether another person or client workspace recorded it. A PDF comparison cannot establish that money has moved.
Before deleting, withholding, or reversing anything, resolve the finding through your normal accounting process. The correct action depends on whether this is a repeat copy, a corrected bill, an existing unpaid entry, or an actual duplicate payment.
Make future reviews easier
Save the invoice number consistently and keep a short note when a corrected document replaces an earlier one. Reuse a verified supplier reference so account changes are easier to see. Keep original files and payment evidence separately from any comparison report.
Vault Mail checks two invoices at a time and flags matching supplier names and invoice numbers. It does not search an accounting platform or audit a complete ledger.
Compare a possible duplicate invoice or see how local invoice comparison works.