5 key tracking mistakes the UK's fastest-growing brands are making right now

Earlier this month, we audited the FEBE Growth 100's ecommerce brands and found that 100% of them had broken conversion tracking on Meta, Google Ads or GA4 - see the full findings here. 

Of the 100 fast-growing UK businesses on the list, 54 have a traditional ecommerce funnel that could be tested in full, and every single one had at least one issue.

So what's actually going wrong?

Here are the 5 tracking mistakes we saw over and over again, and what they actually mean for the businesses running them.

1. Missing key parameters (89% of brands)

The most common issue by a wide margin was missing key parameters, which impacted 89% of the ecom brands on the FEBE Growth 100 list (48 sites). 

This means a conversion event fires to Google Ads, Meta and/or GA4 (the platforms we tested), but it arrives without a piece of information the platform needs to actually use it, like value, currency, content ID, or, most often, Meta's external_id.

Without external_id, Meta can't match the event to a specific customer, which limits Advantage+ targeting and audience building. Without value or currency, platforms also can't do value-based bidding - they know something happened, but not whether it was worth £5 or £500.

This was overwhelmingly a Meta problem in our audit: 44 of the 46 affected brands' Meta issues came down to missing parameters. 

2. Google Consent Mode issues (50% of brands)

Exactly half the brands we audited had Consent Mode implemented incorrectly - that’s 27 of the 54 brands (50%). 

Two patterns showed up repeatedly: Consent Mode's own signal marked as “granted” before the user had actually consented, and sites stuck on Basic Consent Mode, which blocks measurement entirely for anyone who hasn't opted in, rather than modelling it.

Basic mode is compliant, but it's also a straightforward trade of measurement accuracy for implementation simplicity - and most brands running it don't realise they've made that trade. 

The first issue is the more serious of the two, however. If a platform is told consent is "granted" before someone has actually agreed, it starts collecting and using their data without permission - and if that visitor goes on to decline, the data already sent in that window doesn't get undone. That’s a compliance breach.

3. Missing events (48% of brands)

26 of the 54 brands we audited (48%) had at least one core ecommerce event - page view, product view, add to cart, begin checkout, or purchase - missing entirely. 

This was most common on Google Ads, where view_item or add_to_cart were often absent across the whole visit.

Missing events create blind spots in the funnel, causing gaps in reporting and preventing ad platforms from optimising delivery and bidding on site interactions. On Google Ads specifically, a missing view_item or add_to_cart means PMax has no purchase graph to learn from for that stage - it's optimising blind.

4. Duplicate events (41% of brands)

41% of brands (22 sites) had the same customer action - usually a page view or item view - firing more than once with the same event ID, for the same page load. This was heavily concentrated on GA4.

Duplicates inflate whatever the platform reports as a conversion, which distorts attribution and leads to optimising against numbers that are simply higher than what actually happened. It's a quieter problem than a missing event, because the data isn't absent - it's just wrong.

5. Cookie consent issues (32% of brands)

Cookie consent issues were the least common but arguably the most exposed one - affecting 32% of brands (17 sites). These sites had non-essential tracking firing before the user gave consent, or after they'd declined it - in some cases from a consent banner that was present on the page but never actually wired up to block anything.

This creates inconsistent data once a consent framework starts suppressing or altering what fires later in the visit. It's the smallest number on this list, but it's the one issue here with a genuine legal risk.

What happens when they overlap

These 5 mistakes rarely happen in isolation. 80% of the brands we audited had more than one at the same time, and 4% had all 5 issues simultaneously. 

When several tracking issues show up together, the problems aren't confined to one part of the system. A brand might be missing an entire event on one platform, sending duplicated data on another, and firing before consent on a third - each hitting a different link in the chain.

The more of these that stack up, the less of what reaches Meta, Google Ads or GA4 can actually be trusted - and that really matters. 

You can find the full breakdown from the audits here. 

If you want to know which of these 5 tracking mistakes show up on your own site, get in touch and we'll run the same audit.

If you're on the FEBE Growth 100, we've already run it - ask us and we'll share your results directly.