Catch the duplicate before the payment, not after.

Duplicate invoices are one of the most common sources of overpayment in AP. A vendor resends, a copy gets forwarded, and the same bill enters the queue twice. A team processing thousands of invoices a month cannot eyeball every one against the last ninety days of history.

1. 1Webhook trigger starts the run when a new invoice arrives.
2. 2Data Table block looks up the workflow's own ledger of already-processed invoices for the same vendor.
3. 3Code block scores each candidate on invoice number, amount, and date proximity, and returns a confidence value.
4. 4Condition block routes anything above the duplicate threshold to review, and lets clean invoices continue.
5. 5Approval block sends the flagged pair to a human side by side and records the confirm-or-dismiss decision.
6. 6Data Table block writes the outcome back to the ledger so the next run sees it.

The scoring is repeatable: the same two invoices score the same way every time, and the reason a pair was flagged is recorded alongside the human decision. You stop paying twice, and you can prove the control ran.