Key Takeaways
- Why: Without attributed conversions, Google Ads optimizes for clicks; with them, it optimizes for inquiries and sales, which can double the cost per acquisition.
- Two options: Import key GA4 events into Google Ads (simple, single source of truth) or set up the Google Ads conversion tag in Tag Manager (independent, faster, dynamic values).
- Essential in 2026: Consent Mode v2 and advanced conversions; otherwise, a growing proportion of conversions will neither be measured nor modeled.
- Check: Check the Tag Manager and Tag Assistant, then the “Tracking Status” column in Google Ads; never run an automated bidding strategy on unverified tracking.
A Google Ads campaign without conversion tracking is impossible to manage: automated bidding has nothing to optimize, reports show only clicks, and the budget is distributed randomly between what works and what doesn't. Google Tag Manager is the standard tool for setting up this tracking without having to modify the code every time a change is made. This guide describes the two ways to track conversions, the detailed configuration, and the settings that have become mandatory as of 2024.
Choose between GA4 import and the Google Ads tag
| Criterion | Importing GA4 Key Events | Google Ads Conversion Tag in Tag Manager |
|---|---|---|
| Setup | Event already tracked in GA4, GA4-Ads link, import in three clicks | Tag, trigger, and conversion ID to be configured per action |
| Source of Truth | Unique: GA4 and Ads use the same definitions | Double: Ads notes that discrepancies with GA4 are normal |
| Allocation | Model GA4, GA4 window | Google Ads model and window, which more accurately reflect ad clicks |
| Report Submission Deadline | Up to 24 hours | A few hours |
| Dynamic value (cart total) | If the GA4 event has the value | Through a Tag Manager variable read from the dataLayer |
| Advanced Conversions | Available via the Google tag | Possible; configure in the tag |
| Remarketing | Shared GA4 Audiences | Dedicated Ads Remarketing Tag |
For an SME that already tracks its forms in GA4, importing is the simplest option and avoids duplicate definitions. The direct Google Ads tag is recommended for e-commerce sites (with precise transaction values and IDs), for accounts managed by an agency that doesn’t have access to GA4, or when you want a stricter click-based attribution. Both can coexist, provided that only one is used as the “primary” conversion for auctions. Details on the Google Ads side can be found in Defining Google Ads Conversions.
Set up the Google Ads conversion tag in Tag Manager
- Create a conversion action in Google Ads: Goals, Conversions, new “website” action: select the category (lead, purchase, call), the value (fixed or dynamic), the counting method (one per click for a form, all for a purchase), and the conversion window. Google provides an ID (AW-XXXXXXX) and a label.
- Check the Google tag: A Google tag with the identifier AW or G must be triggered on all pages; it contains the conversion linker, which stores the click ID. Without it, conversions are not attributed.
- Create the conversion tag: "Google Ads Conversion Tracking" type: Enter the ID, description, value, and currency (which may vary if dynamic), and the transaction ID to deduplicate purchases.
- Define the trigger: thank-you page (URL contains /thank-you), submission of a validated form, dataLayer event (purchase), click on a "tel:" link. The trigger must be exclusive: only one trigger per actual conversion.
- Test: Preview mode: Perform the conversion, verify that the tag fires once with the correct value; Tag Assistant confirms receipt on Google's end.
- Publish and wait for the action status to change from “unverified” to “conversions being recorded” in Google Ads, which usually takes 24 to 48 hours.
Consent Mode and Advanced Conversions
Two factors determine the quality of monitoring in Europe:
- Consent Mode v2: Required as of March 2024 to use remarketing and conversion tracking in the European Economic Area. The cookie banner sends the ad_storage, ad_user_data, and ad_personalization statuses to Tag Manager; Google Ads tags automatically comply with these. In advanced mode, Google receives cookie-less signals and models conversions for users who have opted out, which generally recovers 10 to 30% of lost conversions.
- Advanced Conversions: The tag sends the data that the user has entered (email, phone number)—in hashed form—to attribute the conversion to a logged-in Google account. They are activated in the conversion action and then in the Tag Manager tag, with variables pointing to the form fields or the dataLayer. This improves measurement accuracy by approximately 5 to 15%, and they are required for certain bidding features.
French law requires prior consent; the consent mode does not eliminate the need for a banner; rather, it links it to the tags. The requirements are outlined in GA4 and GDPR, and apply equally to Google Ads.
Remarketing and Audiences
Remarketing relies on the same Google tag: once it’s placed on all pages, Google Ads creates audience lists (site visitors, product page visitors, abandoned cart users) directly from its interface, without any additional tags. Dynamic parameters (product ID, value) are added for dynamic e-commerce remarketing via a dedicated remarketing tag fed by the dataLayer. The use cases are detailed in Google Ads remarketing.
Common Errors and Checks
| Symptom in Google Ads | Probable cause | Correction |
|---|---|---|
| "Unverified" status after one week | Tag never triggered, invalid ID, trigger set on a URL that does not exist | Tag Manager Overview: Please verify the exact URL of the page. Thank you. |
| Twice as many conversions as forms received | Tag triggered when the "Thank You" page reloads or each time the button is clicked | Count "one per click," single trigger, exclude reloads |
| Meaningless Conversions | Variable with an empty value or dataLayer pushed after the tag | Check the order of events; fixed default value |
| Sharp Drop in Conversions | Website redesign, "Thank You" page renamed, cookie banner updated | Conversion volume alert; retest after each update |
| GA4 vs. Google Ads discrepancy of 20–40% | Different windows and assignment models, consent | Normal; choose a source to guide you and stick to it |
| Conversions attributed to "(undefined)" | No conversion link, cross-domain cookies blocked | Enable the conversion linker; configure the linked domains |
Once tracking has been verified, enable automatic bidding strategies for conversions; see automatic bidding. And keep an eye on conversion volume over time: a 50% drop on a Monday morning is almost always a tagging issue, not a market issue. A reporting tool that links Google Ads spending with GA4 conversions lets you detect these spikes without having to open both interfaces.
How GreenRed Can Help You
Instead of juggling multiple tools, GreenRed's SEA Monitoring and Optimization Module brings these metrics together in a single dashboard, compares them over time, and shows you which actions to prioritize. You can try it for free—no credit card required—from the page Rates.
Frequently Asked Questions
Should I install the Google Ads tag if conversions are already tracked in GA4?
Not necessarily. Linking GA4 to Google Ads and importing key events is sufficient for most small and medium-sized businesses, with a single conversion definition. The direct Google Ads tag provides faster data reporting, stricter click-based attribution, and precise dynamic values, making it the preferred option for e-commerce or high-volume accounts.
Why don't Google Ads and GA4 show the same number of conversions?
Because they don’t use the same conversion window, the same attribution model, or the same recording date: Google Ads attributes the conversion to the date of the click, while GA4 attributes it to the date of the event. A discrepancy of 20 to 40% is common. You need to choose one source for decision-making and stick with it.
Is consent mode required for Google Ads tracking?
Yes, within the European Economic Area, as of March 2024. Without Consent Mode v2 properly integrated with the cookie banner, Google Ads cannot use remarketing audiences or model conversions for users who reject cookies. Tracking continues to work for users who accept cookies, but at a reduced volume.
What are advanced conversions, and should you enable them?
Advanced conversions send Google—in hashed form—the email address or phone number entered by the user during the conversion to improve attribution to the ad click. They typically generate an additional 5 to 15% in conversions and are required for certain features. Enable them if your privacy policy mentions this data processing.