Google Ads & GA4 Conversion Tracking Case Study11 GTM Tags for Calls, Leads & Enhanced Conversions

Google Ads Smart Bidding learns from the conversions you send it. If booking requests and calls are not tracked, or are tracked inaccurately, the algorithm has nothing reliable to learn from and spends budget on clicks that look cheap rather than clicks that become customers.

For a local service like auto detailing, almost every customer either fills in a booking request or taps to call. Measuring both actions correctly, in both Google Ads and GA4, is the foundation every other optimisation is built on.

• The booking form confirmed submissions without loading a new page, so a thank-you page trigger could never fire
• Phone number taps on mobile were not tracked, even though many customers call instead of filling in the form
• No website call conversion, so Google Ads could not see calls made from the site after an ad click
• No Enhanced Conversions, so leads could not be matched back to clicks when browsers limited cookies
• GA4 and Google Ads reported different numbers because they were not fed from the same events

• Google Tag for Google Ads, fired on Initialization so it loads before any other Google Ads tag
• Conversion Linker on all pages, which stores the ad click ID so conversions can be attributed to the right click
• generate_lead conversion for Google Ads, fired by a history-change trigger that only matches when the booking request is complete
• phone_number_click conversion for Google Ads, fired by a click trigger on every tel: link
• Calls from Website conversion, which swaps in a Google forwarding number and records calls placed after an ad click
• Enhanced Conversion data capture plus a User-Provided Data event, so hashed email and phone details are sent with each lead
• GA4 Google Tag on all pages, with generate_lead and phone_number_click as GA4 events using the same triggers as Google Ads
• Microsoft Clarity on all pages for session recordings and heatmaps of how visitors use the booking form

Many modern booking forms submit without loading a separate thank-you page. Instead, the website updates its address in the background when the request is complete. A standard form-submission trigger would fire on failed attempts too, and a page-view trigger would never fire at all.

The solution was a History Change trigger that listens for that background address change and only fires when it matches the completed-request state. That gives one clean lead conversion per real booking request, with no duplicates and no false positives.

Browsers increasingly limit cookies, which means some conversions can no longer be matched back to the ad click that started them. Enhanced Conversions fixes this by sending the email address and phone number entered in the form, securely hashed, alongside the conversion.

Google matches that hashed data to signed-in Google accounts, recovering conversions that would otherwise be lost. The data is captured with a small custom script and passed through a User-Provided Data tag that fires on the same completed-request trigger as the lead conversion.

• Every tag checked in GTM Preview mode, submitting real test bookings and tapping phone links on desktop and mobile
• Google Tag Assistant used to confirm each conversion fired once, with the correct conversion label
• GA4 DebugView used to confirm generate_lead and phone_number_click arrived with the right parameters
• Google Ads conversion diagnostics and Enhanced Conversions status checked after publishing

Every booking request and phone call is now attributed to the campaign, keyword and ad that produced it, in both Google Ads and GA4. Smart Bidding can optimise toward real leads instead of clicks, and the owner can finally see which ads bring in customers and which only spend money.