Spot duplicate invoices before payment: a four-field check

A second invoice with the same number is not automatically wrong. It may be a correction, an instalment or a different transaction. The risk starts when the similarity is missed and a payment is released without checking the job or earlier payment.

This article describes a practical workflow for the German business context. It is not legal, tax or fraud advice.

Four useful search anchors

Section 14 of the German VAT Act lists, among other items, a sequential invoice number, supplier, service details, consideration and tax amount. These details are not an automatic duplicate alarm, but supplier, invoice number, document date and total are useful starting points.

Compare both documents

The helper compares only the four entered fields. It uploads and stores nothing; it does not decide whether an invoice may be paid.

A small exception route

1. Pause the payment and mark the entry for clarification.
2. Find the first document by supplier and invoice number.
3. Name the difference: correction, part invoice, second delivery or unclear amount.
4. Record who decided and which source supports that decision.
5. Keep originals. Section 14b of the German VAT Act regulates invoice retention; seek professional guidance for your case.

:::qa title="Questions"

Is the number enough?

No. It is a strong search anchor, not a decision. Check supplier, job, amount, version and payment status.

Does this tool detect fraud?

No. It compares manually entered fields locally and does not replace an internal or professional review. :::