Most GA4 setup guides walk you through the technical steps. This one starts somewhere different: what you are actually trying to do.
If you run Google Ads, the goal of GA4 conversion tracking is not just measurement. It is Smart Bidding signal quality. Every conversion action you import from GA4 to Google Ads becomes an input for tCPA and tROAS algorithms. Get that signal wrong and you are training your bidding algorithm on corrupted data.
Here is what to configure, what to avoid, and how to verify it is working before you let the algorithm run on it.
Why GA4 Conversion Tracking Is Different From Universal Analytics
Universal Analytics tracked sessions and goals. GA4 tracks events. Everything is an event now: page views, clicks, form submissions, purchases. That flexibility is powerful but also the source of most setup errors.
The biggest difference for paid search teams: GA4 does not have a built-in concept of a macro conversion versus a micro conversion. You have to make that distinction yourself by flagging which events are actual conversions versus soft engagement signals.
If you import every event as a conversion to Google Ads, Smart Bidding tries to convert everyone. That is the same as converting for nothing. We see this in probably half the accounts we audit.
The Events That Actually Matter for Paid Search Optimization
For lead gen: the form submission event (whatever you have named it), a qualified lead event if your CRM passes that signal back, and a phone call event if calls are a real conversion path for your business.
For ecommerce: purchase is the primary signal. Add to cart and begin checkout are useful for remarketing audiences but should not be imported to Google Ads as primary conversions. Bidding to add-to-cart inflates volume but degrades purchase ROAS. We have seen accounts where 80% of Smart Bidding spend was chasing add-to-cart events that never converted.
Google recommends importing only your most important conversion action as the primary optimized conversion. Secondary conversions can be imported as observation-only. Most accounts ignore this and wonder why Smart Bidding is inconsistent.
How to Configure GA4 Events and Import Them to Google Ads
In GA4: go to Admin, then Events, find your conversion event, and toggle Mark as Conversion to on. That makes it available for import.
In Google Ads: go to Tools, then Conversions, then Import, then Google Analytics 4 properties. Select your property, then select the specific GA4 conversion. Do not import all conversions. Choose only the ones you intend to optimize toward.
One important setting: attribution model. GA4 defaults to data-driven attribution if you have enough conversion volume (500 or more per month per conversion action). Below that threshold, it falls back to last click. Check which model is active on your import and document it. Attribution changes can move Smart Bidding performance significantly, and it is easy to forget you made the change.
The Three Mistakes That Break Smart Bidding
Mistake one: importing page views or scroll events as conversions. This happens when someone marks everything in GA4 as a conversion to see what gets tracked, then forgets to unmark them before importing to Google Ads. The algorithm sees a 90% conversion rate and has no idea what a real lead looks like.
Mistake two: using cross-account conversion tracking inconsistently. If you have GA4 conversions and Google Ads direct conversion tracking both firing on the same thank-you page, you will see double-counting in your Google Ads reporting. Smart Bidding counts both. Your actual cost per conversion is 2x what the dashboard shows.
Mistake three: changing the primary conversion action after the campaign has been running. Smart Bidding takes 1 to 2 weeks to relearn after a major signal change. Changing conversion actions mid-campaign triggers a new learning period and usually causes a short-term performance drop. Plan conversion action changes before campaigns launch, not after.
How to Verify Your Conversion Tracking Is Accurate
The fastest verification: run a test conversion yourself. Submit the form, complete the checkout, or trigger whatever event you are tracking. Then check GA4 real-time events to confirm it fired, and check Google Ads conversion tracking to confirm it was counted.
For ongoing accuracy: compare GA4 conversion count with your CRM or backend order system monthly. A 10 to 15% discrepancy is normal (ad blockers, consent issues, attribution windows). A 30% or higher discrepancy means something is broken.
Tag Assistant and the GA4 DebugView are the best tools for real-time event verification. Both are free. Most teams do not use them regularly enough, which is how broken tracking stays broken for months.
Server-Side Tracking: When You Need It and When You Don't
Server-side tracking sends conversion events from your server to GA4 and Google Ads rather than from the user's browser. The benefit: it is not blocked by ad blockers, not affected by browser restrictions on cookies, and not lost when users navigate away before the browser tag fires.
You need server-side tracking if you are running Meta Ads at meaningful scale (CAPI is now essentially required for accurate attribution), if your conversion rate looks lower than your backend numbers suggest, or if you have seen a 20% or higher gap between browser-tracked and actual conversions.
You probably do not need full server-side tracking if your account is primarily Google Search with simple thank-you page conversions and your verification tests show accurate firing. Browser-side tracking is fine for many accounts. Do not add complexity you do not need.
How to Build a Conversion Tracking Audit Checklist
Run through this in order. First: list every active conversion action in Google Ads. Note whether each is Primary or Secondary. Delete any that should not be there. If you are not sure what an action is, that is a sign it should not be there.
Second: for each primary conversion, verify it is firing on the correct event and not on a pageview or a button click that does not complete the form. Third: compare Google Ads conversion volume to your CRM or backend for the last 30 days. Flag any discrepancy above 20%.
Fourth: check your attribution model. If you are on last click and have 500 or more monthly conversions, switch to data-driven and document the change. Fifth: verify GA4 and Google Ads are not double-counting the same conversion. Run the test conversion and check both dashboards simultaneously.