Why GA4 audits matter
GA4 is more flexible than Universal Analytics — but that flexibility comes with more ways to get things wrong. Unlike UA, GA4 doesn't send you warnings when events are misconfigured or when consent mode is missing. You only find out when you notice your conversion numbers don't add up.
In auditing hundreds of GA4 properties, the most common finding is that companies are making marketing decisions on data that's 30–50% incomplete. This leads to under-funded campaigns, wrong attribution, and misdirected ad spend.
1. Duplicate event tracking
Duplicate events are the most common GA4 issue. They happen when GA4 is installed both via GTM and directly in the page code, or when a GTM tag fires multiple times on a single page load. Duplicates inflate session counts, corrupt conversion rates, and make your reports untrustworthy.
Check: Open GA4 DebugView and navigate through your site. If you see page_view events firing twice for a single page load, you have a duplicate.
2. Missing consent mode
As covered above, missing Consent Mode v2 causes 30–70% conversion underreporting in EU markets. If you're running Google Ads campaigns targeting EU users and don't have consent mode set up, this is your highest-priority fix.
Check: Look for a gtag('consent', 'default') call in your page source that fires before the GTM snippet.
3. Wrong data retention settings
GA4 defaults to 2 months of event data retention. This means user-level reports, cohort analysis, and any exploration reports older than 2 months show no data. For most businesses, 14 months is the correct setting.
Fix: Go to GA4 Admin → Data Settings → Data Retention → Change 'Event data retention' to 14 months.
4. Internal traffic not filtered
Internal traffic (from your office, agency, or developer IP addresses) contaminates your data. High-frequency internal browsing inflates session counts and distorts engagement metrics. If your team visits the site regularly, you need an internal traffic filter.
Fix: GA4 Admin → Data Streams → Configure tag settings → Define internal traffic. Then activate the filter under Data Settings → Data Filters.
5. Key events not configured
GA4 tracks all events, but only events marked as 'key events' (formerly conversions) appear in Google Ads campaign reporting and feed Smart Bidding. If your purchase, generate_lead, or sign_up events aren't marked as key events, Google Ads is optimizing blind.
Fix: GA4 Admin → Events → Find the event → Toggle 'Mark as key event'.
The remaining 7 issues
The other seven common issues include: missing referral exclusions (payment gateways appearing as top referrers), high direct traffic (masking true channel attribution), unhealthy traffic sources (bot traffic or spam referrals), missing cross-domain tracking, wrong timezone/currency settings, inactive data streams, and missing Google Ads account linking.
Running a CheckMyTracking audit will surface all of these issues and prioritize them by business impact, so you know exactly where to focus your effort.