Open the traffic acquisition report of almost any UK online store and you'll find Klarna, Clearpay or PayPal listed as a referral source, often with a conversion rate that would make any channel manager jealous. 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 session from a new referral, and the purchase lands in it.
So a customer who clicked a Google Shopping ad, browsed, and paid with Klarna shows up as a referral from Klarna. Paid search looks weaker than it is, and Google Ads gets fewer conversions to learn from.
In the UK there's a second version of the same problem. Since strong customer authentication became mandatory for online card payments, many customers are sent to their bank's app or a 3-D Secure page to approve the payment.
Those domains come back as referrers too, which is why a bank or a card scheme can appear in the report with a handful of sessions and a perfect conversion rate.
How to spot it.
- Open Reports, then Acquisition, then Traffic acquisition, and set the dimension to session source.
- Look for payment names: Klarna, Clearpay, PayPal, Stripe, Checkout.com, Adyen, Worldpay, Apple Pay, Google Pay, a bank, or a domain with "3ds", "acs" or "secure" in it.
- A conversion rate far above the site's average, with sessions that start on the confirmation page, confirms it.
The fix.
GA4 has a setting for exactly this. In Admin, open the web data stream, then Configure tag settings, then Show more, then List unwanted referrals. Add each payment domain. From then on, a visitor arriving from one of those domains keeps the session and source they had before they left.
Three things to know:
- It isn't retroactive. Past purchases stay with the payment provider. Fix it now rather than after the next big campaign.
- Match the domain, not the brand. Providers use several domains, and the one that sends the customer back isn't always the obvious one. The referrals report shows which.
- Shopify is different. Its checkout and Shop Pay run on Shopify's own domains, and the storefront and checkout need setting up together. The Shopify GA4 setup covers that.
What else moves the credit.
Payment referrals are the most visible attribution leak but not the only one. Payment pages on another domain of your own need cross-domain tracking.
A confirmation page that reloads can count the purchase twice, covered in duplicate conversions in GA4. Campaigns without proper tags end up in Direct. And VAT inside revenue inflates every order's value by a sixth.
What to check.
- Place a test order with each payment method you offer, and watch which session source the purchase lands in.
- Compare purchases by source for a month with the payment mix from the platform. If PayPal's share of orders in GA4 is close to its share of payments, it's being credited as a channel.
- After adding the domains, repeat the test orders.
This is one of the checks in the GA4 mini audit. Marc Alexander sets up and fixes GA4 for ecommerce for UK stores.
