Enhanced conversions not working? Why the toggle isn’t enough
When enhanced conversions aren’t working, it usually comes down to one gap: the setting was ticked in Google Ads and the tag was never given any customer data to send. The tick tells Google to expect hashed email addresses and phone numbers, and something on your website still has to supply them.
Treat this page as a fault-finder. Begin with what the diagnostics are telling you, then rule out the causes in order, starting with the ones that don’t need a developer.
What are the diagnostics telling you?
Google’s diagnostics appear about 48 hours after implementing, so a blank screen the morning after a change isn’t evidence of anything. Once that time has passed, match what you’re seeing against this table.
| What you see | Likely cause | Check first |
|---|---|---|
| Nothing yet, and the change is under 48 hours old | Too early to tell | Leave it alone and look again later |
| A prompt about customer data terms | The terms haven’t been accepted | Conversion settings in Google Ads |
| Setting on, no customer data arriving | The tag isn’t configured to send any | The Google tag in GTM |
| Data on some conversions only | A selector or variable fails on certain forms, or visitors declined consent | GTM Preview on each form |
| A warning about the method, or data not processed | Google Ads and the tag disagree about how data is sent | Compare the two settings |
| Coverage fell after a release | Form markup or the cookie banner changed | Recent changes to the site |
Why isn’t ticking the box in Google Ads enough?
“Turn on enhanced conversions” is an account-level instruction. It changes nothing on your website, in the same way that telling the post office to expect a parcel doesn’t post one.
The real work happens in GTM, where you enable “Allow user provided data capabilities” on the Google tag and pick a collection method. Customer data terms have to be accepted first, which is easy to miss when the person with admin access isn’t the person doing the tagging.
The account and the tag also have to agree with each other. Google warns that if you send data in a way different from what you selected in Google Ads it “may not be processed”, so a perfectly tidy implementation can be discarded because the account was expecting something else. If you’ve changed approach at any point, this is the first place to look.
Which GTM method should you use?
GTM gives you three ways to collect the data, and they fail in quite different ways.
| Method | How it works | Where it goes wrong |
|---|---|---|
| Automatically detect | Google looks for email and phone values on the page | Unusual or embedded forms, and pages where the value has gone by the time the tag runs |
| CSS selectors or JavaScript variables | You say exactly where each value lives | Selectors break when markup changes, while variables only break if the code behind them does |
| Code snippet | A developer passes the values in directly | Needs site access and someone to look after it |
We’d normally push the email and phone number into the data layer at the moment of submission and read them with a JavaScript variable in GTM. That doesn’t depend on page layout, and you can see the values in Preview mode before anything goes live. Automatic detection is fine for a quick trial, although it’s the one we’d trust least on a form that matters.
Timing catches people out more often than the choice of method. A conversion tag commonly fires on the thank-you page, by which point the form and its email field no longer exist. Either fire the tag on the submission event while the value is still available, or have your server output it on the confirmation page. Keep personal data out of the URL in both cases, as anything in a query string ends up in logs and analytics reports.
How do you set up enhanced conversions in GTM?
- Accept the customer data terms and turn on enhanced conversions in Google Ads, noting the method you select.
- In GTM, open the Google tag and enable “Allow user provided data capabilities”.
- Choose your collection method and map the email address, plus the phone number if you collect one.
- Check the conversion tag too, as some containers give it a separate option to include user-provided data.
- Open Preview mode, submit a real test enquiry or order, and read the values the tag actually received.
- Publish, make a note of the date, and give diagnostics about 48 hours before you judge the result.
What format should the data be in?
Badly formatted data rarely throws an error, so it tends to surface later as poor matching. Check these against what the tag receives, and not against what the form appears to contain.
- Email: trimmed of spaces and in lower case. A stray space left by autofill is enough to produce a different hash if you hash the value yourself.
- Phone: international format with the country code, so
+447700900123instead of07700 900123. Most UK forms collect the second version, so it usually needs converting. - Empty values: look out for
undefined,nullor a placeholder such as “Enter your email” being passed along as though it were real data. - Hashing: the tag normally handles this for plain values. If your own code hashes first, it needs to be SHA-256 on the normalised value and sent as hashed data, because a hash of a hash matches nobody.
Test with more than one form as well. A site with a contact form, a quote form and a checkout can easily have one working perfectly and two sending blanks, and the overall coverage figure won’t tell you which is which.
Can consent stop enhanced conversions working?
Yes, and sometimes that’s the system behaving correctly. If ad_user_data is denied, the hashed data isn’t collected, so a healthy set-up with plenty of visitors declining will still show partial coverage.
The fault to look for is a banner that never sends ad_user_data at all, which tends to happen on integrations built before Consent Mode v2. Check that in Preview mode before you rewrite any tags, and read how the four Consent Mode signals work in the UK if those names are new to you.
What about enhanced conversions for leads?
Google said web and leads would be combined into a single on/off setting starting June 2026, with tags, Data Manager and API accepted together from April 2026. Older guides showing two separate switches may no longer match the screen in front of you.
Google also describes its classic offline conversion import as a legacy feature and recommends upgrading to enhanced conversions for leads. If your uploads come from your own code, the move to the Data Manager API may affect you as well.
How much will enhanced conversions improve results?
You’ll see percentages quoted around the internet. We couldn’t verify any official Google uplift figure, so we’re not going to hand you one. What you get depends on how many of your conversions come with an email address or phone number, how many visitors consent and how much your bidding relies on the extra signal.
If you’d rather hand over the fight with the container, our enhanced conversions setup covers the tag, the data mapping and the testing inside your own GTM account. It starts from £750 at a fixed price, and you’re welcome to talk it through with us first.