<b>Q: My purchase event fires twice and inflates revenue. How do I de-dupe it?</b>

<b>Q: My purchase event fires twice and inflates revenue. How do I de-dupe it?</b>

A: GA4 won't auto-dedupe purchases unless you give it a transaction_id.
— Send a unique <code>transaction_id</code> on every purchase event. GA4 drops repeats of the same id within a session window.
— Check it's actually arriving: DebugView → click the purchase event → confirm transaction_id is present and unique.
— The classic double-fire is a thank-you page reload plus a GTM trigger both firing. Trigger purchase only once, on dataLayer push, not on page_view.

TL;DR: Always send a unique transaction_id, and fire purchase on the dataLayer event, not page load.

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