Open the traffic acquisition report of almost any Australian online store and you'll find Afterpay, Zip or PayPal listed as a referral source, often with a remarkably high conversion rate. They didn't bring you those customers. Your campaigns did, and GA4 has given the credit away.
Why it happens.
With buy now, pay later and wallet payments, the customer leaves your checkout, approves the payment on the provider's site, and is sent back to your confirmation page. When they arrive back, the browser reports the provider as where they came from. GA4 treats that as a new referral, and the purchase is credited to it.
So a customer who clicked a Google ad, browsed, and paid with Afterpay shows up as a referral from Afterpay. Paid search looks weaker than it is, and Google Ads gets fewer conversions to learn from.
How big the problem is.
It grows with how popular these options are among your customers. In Australia, where buy now, pay later is widely used, a store can see a large share of its online revenue credited to payment providers. Card payments through 3-D Secure checks can cause the same problem when the bank's page sits between checkout and confirmation.
The fix.
- Find the domains. In GA4's traffic acquisition report, set the dimension to session source and look for payment providers, bank verification pages and the store platform's own checkout domain.
- Add them to unwanted referrals. In GA4, go to Admin, Data streams, your web stream, Configure tag settings, then List unwanted referrals. Add each domain.
- Test it. Place an order with each payment method and check that the purchase keeps the original source.
- Check Google Ads. Once purchases stop leaking to referrals, conversions credited to ads should rise. Tell whoever runs your campaigns, so they know why.
The change applies from when you make it. Past data stays as it was, so note the date for anyone comparing months later.
Related problems at checkout.
- Purchases counted twice when customers reload the confirmation page, or return to it from an email. A unique transaction ID on every order fixes that. See fixing duplicate purchases in GA4.
- Missing purchases on one payment method, because its confirmation page works differently. Test each method, not just card.
- Revenue with GST included, covered in GST and GA4 revenue.
Marc Alexander fixes checkout tracking for Australian stores, including Shopify. The GA4 mini audit checks attribution on every payment route.