Google Ads bidding runs on conversion data. Smart Bidding strategies such as Maximise conversions and Target CPA decide who sees your ads, and how much to bid, based on the conversions you’ve told Google to optimise for. When that data is wrong, the account doesn’t just report badly. It spends your budget chasing the wrong thing, and it does so very efficiently.
The awkward part is that faulty tracking rarely looks broken. The account shows conversions, the numbers look roughly sensible, and nobody checks further. In account audits, conversion tracking is one of the first things we look at, because “conversions are showing” and “conversions are accurate” are two very different things. These are the mistakes that most often sit between them.
Counting one enquiry more than once
Duplicate counting inflates your results and makes whichever campaigns trigger the duplicates look better than they are. The usual causes are:
- the same conversion tag installed twice, for example once in the website’s code and again through Google Tag Manager
- a tag on a thank-you page that fires again whenever the page is refreshed or revisited
- a Google Ads conversion tag and a GA4 key event imported into Google Ads, both tracking the same form and both set as primary
Then there’s the counting setting. Every conversion action in Google Ads counts either “Every” conversion after an ad click or only “One”. Google recommends “Every” for sales, where each purchase adds value, and “One” for leads, because a second form from the same person after the same click is rarely a second customer (Google’s guide to conversion counting options). A lead form left on “Every” will count someone who submits twice as two enquiries.
A useful sense check is to compare Google Ads with your inbox. Say you received 30 enquiries from the website last month and Google Ads reports 45 form conversions. The figures will never match exactly, partly because Google Ads records conversions against the date of the ad click rather than the date of the enquiry, and partly because not every enquiry comes from an ad. But if Google Ads regularly reports more enquiries than you received, something is being counted twice.
Treating every action as equally important
A newsletter sign-up, a tap on your phone number and a completed quote request are very different things. If all three are primary conversions with the same value, Google Ads treats the sign-up as just as good as a job worth several hundred pounds, and Smart Bidding will chase whichever is easiest to get.
This is what primary and secondary conversion actions are for. Primary actions appear in the Conversions column and are used for bidding. Secondary actions appear in the All conversions column and are there for reporting only (Google’s guide to primary and secondary actions). Decide which actions represent a real business result, usually a completed enquiry form, a call over a sensible length or a booking, and make only those primary. Softer signals can stay as secondary, where you can still see them without the bidding chasing them.
If some primary actions are worth more to you than others, give them different conversion values so bidding knows the difference. A rough estimate based on how often each type of enquiry turns into paid work is fine to start with.
Counting clicks instead of enquiries
Some conversion actions measure interest rather than an enquiry: a visit to the contact page, a click on a “Get a quote” button that only opens the form, a tap on a phone number. They’re easy to set up and they fire often, which makes the account look busy. But a visit to the contact page isn’t an enquiry, and a tap on a number doesn’t mean a call connected.
If one of these is your main primary conversion, bidding learns to find people who look around rather than people who get in touch. Move the conversion to the point where the enquiry succeeds: the form’s confirmation message or page, or a call that lasts long enough to be a real conversation.
Leaving phone calls out
For a business where most customers ring rather than fill in a form, missing calls is the biggest gap of all. Google Ads can only optimise towards what it can see, so the conversions column shows a fraction of what the campaign is doing.
Google Ads can track calls from your ads and, with a snippet of code on your site, calls to your website number from people who clicked an ad. Both use Google forwarding numbers, which are available in the UK, and both let you set a minimum call length so short or accidental calls don’t count. We’ve explained these options, and how to track calls from every other channel too, in how to know which marketing is bringing you enquiries.
Ignoring consent mode
In the UK you need a visitor’s consent before using cookies or similar technology for online advertising, and that includes conversion tracking. The ICO’s guidance is blunt: for online advertising purposes “you must get consent. You cannot rely on any of the exceptions” (ICO guidance on storage and access technologies). Google’s own EU user consent policy applies to visitors in the UK as well as the EEA and Switzerland.
Consent mode is how your website tells Google what each visitor chose on your cookie banner. Version 2 added two signals, ad_user_data and ad_personalization, alongside the original ad_storage and analytics_storage. If those signals are missing or wrong, Google can’t confirm consent was given, and it may restrict features such as remarketing and conversion measurement on your account.
Set up properly, consent mode also lets Google model conversions from visitors who declined cookies, so the gap is estimated rather than simply lost. There are two versions. In basic mode, Google’s tags don’t load at all until someone accepts. In advanced mode, the tags load with consent set to denied and send limited signals without cookies, which gives Google more to model from. Which suits your site is worth discussing with whoever manages your cookie banner and privacy notice.
Not using enhanced conversions
Browser privacy settings, declined cookies and people switching devices all mean some conversions can’t be linked back to an ad click. Enhanced conversions help by sending a hashed (scrambled) copy of details the customer entered in your form, such as their email address, which Google matches against signed-in Google accounts.
For lead generation there’s also enhanced conversions for leads. It uses the same hashed form details so that you can later import which enquiries turned into paying customers, letting bidding learn from real sales rather than form fills alone. Enhanced conversions are switched on in your Google Ads conversion settings and set up through the Google tag, Google Tag Manager or the API. Because they use customer data, make sure your privacy notice covers them and that they respect each visitor’s consent choices.
Letting tracking drift after website changes
Many tracking setups are inherited rather than designed. A developer added a generic tag years ago, the account has passed through an agency or two, and nobody has checked since whether the tags still match the site. Then a form is rebuilt with a different plugin, a thank-you page moves or the whole site is redesigned, and tracking stops firing or starts firing in the wrong place. Nothing in the account flags it straight away. The numbers just drift.
Check tracking after every change to your website. If a redesign is coming up, add it to the checklist alongside the SEO points in redesigning your website without losing Google rankings.
How to check your own tracking
You don’t need to be technical to run these checks:
- Look at the tracking status. In Google Ads, the conversions summary under Goals shows a status for each conversion action. “Inactive”, “Unverified” or “Needs attention” all need looking into, and hovering over the status gives you a Troubleshoot option that opens Google’s Tag Assistant.
- Run a test conversion. Using Tag Assistant (Google Tag Manager’s preview mode runs through it too), submit your own form and check that exactly one conversion tag fires, at the right moment, with the right value.
- Check what’s primary. Make sure only real enquiries are primary conversions and that each lead action counts “One”.
- Reconcile every month. Compare Google Ads conversions with the enquiries that reached your inbox and phone. Consistently more in Google Ads points to double counting; far fewer usually means something is missing, often calls.
Getting this right is a small job compared with months of Smart Bidding learning from bad data. It’s part of the work we do with clients, too: the Fire Protection Association mention our help setting up their conversion tracking in their testimonial.
If you’d like a second pair of eyes on your conversion tracking before you change budgets or bidding, request a free Google Ads audit.
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