91.5 million Americans will use Buy Now Pay Later in 2025. Every one of those Klarna, Afterpay, or PayPal redirects is breaking your WooCommerce conversion tracking. The payment goes through. The order confirms. But GA4 never sees the conversion—or worse, credits PayPal.com as the traffic source instead of your ad campaigns.
Here’s the painful irony: BNPL drives 85% higher average order values (Capital One Shopping Research, 2025). You want these customers. You need these customers. But every payment option you add is silently degrading your attribution data.
The Hidden Tracking Disaster Nobody Talks About
The global BNPL market is projected to hit $560.1 billion in 2025—a 13.7% increase from last year (ResearchAndMarkets, 2025). That growth translates directly to more WooCommerce stores adding Klarna, Afterpay, PayPal Pay Later, and Affirm to their checkout pages.
Makes sense. Up to 40% of BNPL sales come from entirely new customers (Capital One Shopping Research, 2025). If you’re not offering flexible payment options, you’re losing sales to competitors who do.
But here’s what those BNPL integration guides don’t mention: every offsite payment gateway creates a tracking black hole.
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Why Offsite Payment Gateways Break Your Tracking
When a customer clicks “Pay with Klarna” or “Checkout with PayPal,” they leave your site. Your browser session ends. A new session begins on klarna.com or paypal.com.
If they return to your thank-you page after payment, GA4 sees it as traffic from klarna.com—not from the Facebook ad or Google search that originally brought them to your store.
That’s the attribution problem, and referral exclusions can fix it. Sort of.
The Real Problem: Events That Never Fire
Referral exclusions tell GA4 to ignore the external domain and maintain the original session. But they only work when the customer actually makes it back to your thank-you page with their tracking intact.
Here’s what actually happens:
- Customer completes BNPL payment: Payment succeeds on Klarna/Afterpay servers
- Redirect initiates: Customer should return to your thank-you page
- Browser interruption: Customer closes tab, loses connection, or gets distracted
- Your tracking: Never fires because thank-you page never loads
The order exists in WooCommerce. The payment cleared. But your analytics have zero record of the conversion.
Referral exclusions can’t recover events that never happened. They only fix attribution for sessions that successfully return—and even then, only if ad blockers and browser privacy features don’t block your tracking scripts.
The Compounding Effect: More Payment Options = Worse Data
Here’s the math that should worry you:
68% of U.S. online shoppers have used PayPal BNPL at least once (Chargeflow, 2025). Add Klarna users, Afterpay users, and Affirm users—and a significant portion of your customers are completing purchases through offsite payment flows.
Every payment option you add to increase conversions simultaneously increases the percentage of orders that slip through your tracking.
This creates a vicious cycle: your best-performing payment methods become your biggest data blind spots. You can’t accurately measure ROAS on the campaigns driving these high-AOV customers because you can’t see the conversions they’re generating.
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Why the “Standard Fix” Doesn’t Actually Fix It
The advice you’ll find everywhere: add referral exclusions for payment domains. PayPal.com, Klarna.com, Afterpay.com, Affirm.com—add them all to your GA4 referral exclusion list.
This addresses attribution. If a customer returns from Klarna, GA4 won’t credit Klarna as the source. The original campaign attribution stays intact.
But referral exclusions don’t work retroactively—only on future traffic (LearnDigitalAdvertising, 2025). More importantly, they assume your thank-you page tracking actually fires.
The WooCommerce Conversion Tracking plugin documentation puts it bluntly: “We don’t support if an offsite payment gateway is in use—those cases can be complex and time consuming to solve.”
Translation: if you’re using BNPL gateways, you’re on your own.
The Real Solution: Fire on Payment, Not Page Load
The fundamental problem with client-side tracking is dependency on browser behavior. Thank-you page loads. JavaScript execution. Session continuity across redirects.
BNPL breaks all of these assumptions. Payments complete server-to-server between the BNPL provider and your store—often before the customer even returns to your site.
Server-side tracking solves this by hooking into WooCommerce’s woocommerce_payment_complete action. This fires the moment payment succeeds—regardless of what the browser does afterward.
Customer closes the tab? Conversion tracked. Customer’s browser blocks scripts? Conversion tracked. Customer gets distracted and never sees the thank-you page? Still tracked.
The payment completion happens on your server. Server-side tracking captures it there—then routes the conversion data to GA4, Facebook CAPI, Google Ads, and everywhere else it needs to go.
How Server-Side Actually Captures BNPL Conversions
Here’s the flow that makes BNPL tracking work:
- Customer selects Klarna at checkout and redirects to Klarna
- Payment completes on Klarna’s servers
- Klarna notifies WooCommerce via webhook/API that payment succeeded
- WooCommerce triggers
woocommerce_payment_completehook - Server-side tracking captures the event immediately
- Conversion data routes to all platforms—GA4, Facebook, Google Ads
The browser might never return. The customer might see a blank page. Doesn’t matter. The conversion event fired at step 5, the moment the payment actually succeeded.
Transmute Engine™ runs as a first-party Node.js server on your subdomain—receiving events from WooCommerce via the inPIPE plugin, then routing them simultaneously to every platform. No GTM. No thank-you page dependencies. Just clean conversion data that actually reflects your sales.
Key Takeaways
- BNPL market hits $560B in 2025: More customers using offsite payment flows means more tracking gaps
- Referral exclusions only fix attribution: They don’t recover events that never fire
- 85% higher AOV from BNPL: Your most valuable customers are the hardest to track
- Thank-you page tracking fails on redirects: Payment completes server-to-server, not in the browser
- Server-side tracking fires on payment completion: Captures conversions regardless of browser behavior
Frequently Asked Questions
When customers redirect to PayPal to complete payment, GA4 starts a new session attributed to paypal.com. Even with referral exclusions, if the customer doesn’t return to your thank-you page—or if their browser blocks the tracking script—the original ad attribution is lost entirely.
Referral exclusions only solve the attribution problem when customers successfully return to your thank-you page. They don’t recover conversion events that never fire because customers closed the tab, got distracted, or had their browser block the tracking script.
Yes, but not with client-side tracking that relies on thank-you page loads. Server-side tracking that hooks into WooCommerce’s woocommerce_payment_complete action fires when payment actually succeeds—regardless of whether the browser returns to your site.
BNPL services like Klarna and Afterpay redirect customers to external domains, breaking the browser session. The payment often completes on the BNPL provider’s servers before the customer returns to your site. If your tracking only fires on thank-you page loads, you’re missing conversions.
Stop losing conversions to payment redirects. See how server-side tracking captures every BNPL purchase at seresa.io.
