Conversion tracking in GA4 is two separate jobs that get conflated: getting the event to fire reliably, and deciding which events deserve to be called conversions. The first is technical. The second is commercial, and it is the one that causes real damage when it goes wrong.
Step 1: Decide what a conversion actually is
A conversion should represent genuine commercial intent — an action that a salesperson would be pleased to see. For most businesses that is a short list: a contact or demo form, a phone call over a meaningful duration, a booking, a qualified application or a purchase.
Newsletter signups, PDF downloads and video views are useful events. They are rarely conversions. Mark them as such and your ad platforms will start optimising to find more people who download PDFs and never buy.
Step 2: Fire the event through Google Tag Manager
Use GTM rather than hard-coding events. The typical setup is a trigger that detects the action, and a GA4 event tag that sends a named event with useful parameters.
For a form submission, the most reliable trigger is usually not GTM’s built-in form submission listener — it misses AJAX forms, which is most modern forms. Better options are:
- A data layer push added by the form plugin on successful submission
- An element visibility trigger on the success or thank-you message
- A page view trigger on a dedicated thank-you URL, where one exists
Send parameters with the event. A form_name or form_location parameter is what later lets you see which form produced which lead, instead of one undifferentiated blob.
Step 3: Track the conversions that are not form fills
Phone calls. Click-to-call on mobile can be tracked as a link click, but that only proves someone tapped the number. For genuine call tracking you need a call tracking provider that records duration, so you can count only calls over, say, 60 seconds.
WhatsApp. Track clicks on the WhatsApp link as an event. It is a click, not a conversation, so treat it as a leading indicator rather than a lead.
Bookings. If your booking tool runs on a separate domain, configure cross-domain measurement first, or the booking will be attributed to a referral from your own site.
Purchases. Use the standard purchase event with the full e-commerce parameter set, including value and currency. Ad platforms rely on this structure.
Step 4: Mark the event as a conversion
In GA4, go to Admin, then Events, and toggle the event to a conversion. The event has to have fired at least once before it appears, so test first.
Step 5: Verify before you trust it
Use DebugView, complete the action yourself, and confirm the event appears with the parameters you expect. Then check for duplicates: the single most common conversion tracking fault we find is the same conversion firing twice, once from a plugin and once from a manually added tag.
A useful sanity check is to compare GA4 conversion counts against the actual records in your CRM or inbox for the same week. If GA4 says 40 and your inbox says 27, you have a tracking problem, not a great month.
Step 6: Send values where you can
A conversion with no value cannot be optimised for return. If you know the average value of a lead type, send it as the event value. Even a rough, agreed estimate is more useful to bidding algorithms than nothing at all.
Where to go from here
The technical part of conversion tracking takes an afternoon. Deciding what counts as a conversion, and defending that decision, is what makes the data usable. If you want a second pair of eyes on your setup, our analytics and tracking team runs a free tracking audit that covers GA4, Google Tag Manager, conversion events, CRM integration and attribution.