Duplicate Invoice Checker
Upload your AP or payment export. Find likely duplicates, review the evidence, and download the flagged pairs.
Free to use · No signup · Your records stay in your browser
Start with an invoice or payment export.
Include vendor, date and amount. Invoice numbers strengthen the match. Import invoices or payments separately, or map a record-type column to distinguish them.
(synthetic data)
Confirm your columns.
Check the source rows, column mappings and formats. Remove totals and subtotals before importing.
Positive and negative amounts are compared separately. Zero amounts are excluded. Currencies are never converted. Record types must use consistent names; different types are kept separate.
Review the flagged pairs.
A flag is a review suggestion, not proof of a duplicate. Check source documents and payment IDs. Overlapping pairs can include the same record, so pair amounts are not added together.
Download the evidence.
The CSV includes both source row numbers, original vendors and references, normalized dates, amounts, risk levels and every reason. It contains sensitive financial records; keep the downloaded file in your usual secure location.
How the matching works.
Vendor names are normalized for case, accents, punctuation and spacing. Invoice numbers are normalized for case and punctuation, preserving leading zeros. Currencies use recognized ISO codes, and amounts are compared exactly at each currency’s decimal precision.
Candidate groups use vendor, reference, currency, record type and amount. Close-date rules use a fixed seven-day window. A spelling variant means one inserted, deleted or substituted character, with at least five characters in each name or reference.
For manual checks, read how to find duplicate invoices in Excel.
High risk
Same normalized vendor, invoice reference, currency and amount, with dates no more than seven days apart.
Medium risk
Same vendor and reference with different amounts or dates farther apart; or exact amount and close dates with a one-character invoice variant; or exact reference and amount with a one-character vendor variant and close dates.
Low risk
Same vendor, currency and amount within seven days, with different or missing references. Legitimate repeat purchases can trigger this rule.
Before you review.
What about recurring monthly charges?
The same vendor charging $500 in successive months with different invoice numbers is not flagged on amount alone. If a reference is reused, the pair appears at medium risk when dates are more than seven days apart. Confirm the billing periods before deciding.
Can I check duplicate payments?
Yes. Import a payment export and map the underlying invoice number when available. A repeated invoice may represent a partial payment or a repeated export row, not two payments. Confirm payment IDs and bank evidence. Keep invoice and payment rows separate, or map a consistently named record-type column.
Are my records uploaded or saved?
No. Files are read by a worker in your browser. Records are never sent to Beckmont or saved in browser storage. Clear the session or close the tab to release the tool’s data. Downloaded files remain on your device.
What can this miss?
It cannot prove fraud or find every duplicate. Unrelated vendor aliases, multi-character typos, different amounts and different references can be missed. It excludes zero amounts and comparisons between different currencies, signs or record types. Very dense candidate groups stop with an error rather than incomplete results: split the export by vendor or period. Limits are one million comparisons and 10,000 flagged pairs.