How to track a conversion on a third-party checkout or booking page
If your payment or booking completes on someone else's domain, a hosted checkout, a booking platform, a payment link, the conversion happens where your tags are not. By default it goes uncounted, or gets credited to the wrong place.
Why the conversion goes missing
Your GA4 and pixels live on your domain. When the final step happens on a third-party domain you often cannot place a tag on, the confirmation event never fires on your side, and the return visit can even show the provider as a referral.
The options, best to worst
- Server-side from a webhook: the most reliable. The provider sends your server a webhook on a completed order, and your server reports the conversion via server-side tracking. No reliance on a tag you cannot place.
- Cross-domain tracking: if you can add your tag on the third-party page, set up cross-domain tracking so the session carries across.
- Return-page event: fire the conversion when the customer lands back on your thank-you page, least reliable, since not everyone returns.
The recommendation
If the provider offers webhooks, use them and report server-side; it captures every completed sale regardless of whether the customer comes back or what their browser blocks. Add the payment domain to your referral exclusions either way so attribution stays with the real source.
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