Google Ads Conversions Look Wrong Since June? Check Your Consent Setup (UK)

Your Google Ads account says conversions are down. Your sales or leads say otherwise. Or the numbers moved in the summer and nobody can say why.

Before you blame the campaigns, check the cookie banner. Since 15 June 2026, one consent setting controls the advertising data your Google Analytics tag can pass to Google Ads. If that setting is wrong, your reports can be wrong. And because Smart Bidding learns from those reports, your bidding can go wrong too.

This article explains what changed, what the UK rules say, and how to check your own setup in about half an hour.

Google Analytics used to have two controls over advertising data. The first was Google Signals, a setting inside Analytics. The second was Consent Mode, which passes your visitor's cookie choices to Google through a signal called ad_storage.

From 15 June 2026, Google says Analytics uses Consent Mode “as the single control” for collecting Google Ads cookies and IDs from the Analytics tag. Google Signals now only controls whether Analytics data is linked to signed-in users for reporting inside Analytics.

In plain English: your cookie banner's answer to “can we store advertising cookies?” is now the one switch that matters for the ad data your Analytics tag passes to Google Ads. When ad_storage is denied, Google Ads works with more limited signals, such as the click ID in the URL.

That is not a problem if your banner is set up correctly. It is a problem if:

• the banner sends “denied” by default and never updates when a visitor accepts,
• the banner updates too late, after the conversion tag has already fired,
• or someone changed the banner, the tag setup or the website, and nobody checked what Google receives.

Before June, two settings shared that job. Now ad_storage carries all the weight, so it deserves a proper check.

In the UK, cookies and similar technologies fall under the Privacy and Electronic Communications Regulations (PECR). The Data (Use and Access) Act 2025 changed PECR, and the ICO published its final guidance on storage and access technologies on 29 April 2026.

Three points matter for advertisers:

1. Advertising still needs consent. The ICO says the use of storage and access technologies “for online advertising purposes requires consent”, and that no advertising purpose is strictly necessary. Measuring ad effectiveness is part of that advertising purpose.
2. Some analytics no longer needs consent, with conditions. There is now an exception for storage used only to collect statistics about your own website. The data cannot be shared except to help improve your service, and visitors must get clear information and an easy way to object. The ICO says that linking a visitor's journey to an online advert needs consent. So analytics that feeds your ad platforms does not fall under the exception.
3. Fines are much higher. The ICO can now issue PECR fines of up to £17.5 million, or 4% of worldwide annual turnover if higher. The previous maximum was £500,000.

None of this means you need a banner that gets fewer people to accept. It means the banner must work properly and give a real choice. For whether your own banner meets the rules, speak to your legal or privacy adviser. The rest of this article is about the measurement side.

Most people think a broken banner means “we under-report conversions”. That is only half of it.

Smart Bidding sets bids from the conversions it can see. If consent is lost evenly across all visitors, it sees fewer conversions, but a fair sample. Consent is rarely lost evenly. A banner can behave differently on mobile and desktop, on different browsers, or on different pages. If the fault hits one group harder, Smart Bidding sees that group as converting worse than it does.

It then does what it is built to do. It can bid down on the people who look weaker and put money into the people who look stronger. The reports look plausible. The spend moves. Nobody notices, because nothing is flagged as broken.

This is why “our tracking is roughly right” is not good enough. For example, a number that is 20% low in one place and accurate in another can steer the whole account. We explain the wider gap between what platforms report and what actually happened in platform ROAS vs incremental ROAS. And if your ad numbers never match your finance numbers, this guide covers the usual reasons.

Consent is one of two common ways bidding gets trained on the wrong data. The other is fake or low-quality leads being counted as conversions. See how fake leads affect Target CPA.

A measurement system you can trust is the foundation for every budget decision. That is what our media measurement framework work is for.

You can do most of this yourself. Allow about half an hour.

1. Check the default state. Open your site in a private window with Google Tag Assistant running. Before you click anything on the banner, check what consent state Google receives. For UK traffic, advertising consent should start as “denied”.
2. Accept, then check again. Click “Accept” and confirm that ad_storage, ad_user_data and ad_personalization change to “granted”. If they stay denied, your Google Ads data is limited for everyone who says yes.
3. Reject, then check tags. In a fresh private window, click “Reject”. Confirm that advertising tags respect the choice. This protects you on the compliance side.
4. Check the order of events. The consent update must reach Google before your conversion tags fire. In Google Tag Manager, the consent overview shows which tags wait for consent. Test a real conversion (a form fill or a test purchase) after accepting, and check it appears in Google Ads.
5. Look at your conversion diagnostics. In Google Ads, open your main conversion actions and check the diagnostics for consent or tag warnings.
6. Compare against your own records. Put Google Ads conversions next to your CRM leads or shop orders, week by week, from May to now. Look for a step change around 15 June 2026 or around any date your banner, website or tags changed. A step change with no matching change in real sales points to tracking, not demand.
7. Watch your consent rate. Your banner tool can usually report how many visitors accept. Track it by device. A sudden drop, or a big gap between mobile and desktop, is a warning sign for the bidding problem above.

For the full list of tracking checks, including double counting and attribution settings, use our free tracking audit checklist.

Fix the setup first, then give the account time. Google says Smart Bidding can take up to around 50 conversions or 3 conversion cycles to settle after a change, so judge the result over that period, not over a few days. Do not change targets and budgets in the same week you fix tracking, or you will not know which change did what.

If the fault ran for months, treat the conversion data from that period with care. Do not use it to set Q4 targets without adjusting for the gap.

• Google Analytics Help: Consent Mode as the single control for Google Ads data (from 15 June 2026)
• Search Engine Land: Google simplifies Analytics and Ads consent rules
• Google Ads Help: Smart Bidding learning period
• ICO: how the storage and access rules apply to online advertising
• ICO: what are the exceptions
• ICO: final storage and access technologies guidance published (29 April 2026)
• ICO: commencement of the Data (Use and Access) Act, PECR fines up to £17.5 million
• ICO: guide to PECR (previous maximum fine of £500,000)