Deduplication

Deduplication identifies records representing the same event or entity under a stated rule and prevents them from being counted twice. In reach measurement, the entity may be a person across devices: Google Ads uses models to deduplicate audiences across sessions, formats, networks and devices.[1] That is a different problem from removing a duplicate delivery of a purchase message.

A store could use a stable order reference to recognise repeat delivery of the same purchase record. Document separately how amendments, refunds and genuinely new orders are handled. Matching amounts or nearby timestamps alone are not a safe reason to merge purchases. Decide first what must be unique: people, orders or technical messages, since each requires a different matching rule.