Start with the obligation
An invoice may be resubmitted with a suffix, a changed reference, or a new date. Preserve the original identifiers and compare the underlying purchase, delivery, service period, quantities, and amounts. A changed invoice number does not establish a separate obligation.
Look for legitimate differences
Similar amounts and descriptions can represent separate valid transactions. Check whether the records cover different service periods, staged deliveries, approved revisions, or separate orders. A matching signal should create a review question rather than an automatic rejection.
Check what actually settled
Compare credits, partial payments, reversals, returned payments, and allocations. The full invoice total may not be the outstanding amount. Retain the source records and calculation supporting the conclusion.
Record the decision
Document the candidate records, evidence checked, finding, reviewer, and required approval. Keep unresolved questions visible and assign follow-up. Use confirmed cases and legitimate lookalikes to improve the next review.