GA4 Audit Guide: How to Verify Your Data Is Actually Accurate

Why GA4 Data Accuracy Matters

GA4 data quality issues are often invisible. Sessions count looks plausible, conversions seem roughly right — but the numbers may be significantly wrong in ways that are not obvious until you do a systematic verification. A GA4 audit examines whether your data is collected correctly, processed without duplication or loss, and attributed accurately.

Step 1: Verify Tag Installation

• Open your website in Chrome, then DevTools then Network tab
• Filter for "collect" or "g/collect" — you should see GA4 requests going to google-analytics.com/g/collect (or your sGTM subdomain)
• Check the request fires on every page, not just specific pages
• Use Google Tag Assistant (browser extension) to verify the GA4 tag is firing correctly and connecting to the right Measurement ID

Step 2: Check for Duplicate Tags

Multiple GA4 tags firing on the same page cause inflated session counts. Look for:

• In the Network tab: multiple requests to /g/collect on a single page load
• In GA4 DebugView: multiple page_view events in rapid succession
• In GA4: unusually high sessions-per-user ratio (above 10 suggests duplicate sessions)

Common causes: GA4 tag in GTM and also hardcoded in the page; GA4 tag firing in multiple GTM containers; tag firing on both All Pages trigger and specific page trigger simultaneously.

Step 3: Validate Conversion Events

For each Key Event (conversion):

1. Complete the conversion action on your site in real-time
2. Open GA4 DebugView immediately
3. Verify the event fires once (not zero, not twice)
4. Check the event parameter values are correct (correct purchase value, correct form name)
5. Compare the GA4 conversion count to your CRM or order management system count over the same period

A 10-20% discrepancy between GA4 and CRM is expected (browser cache, navigation issues). A 30%+ discrepancy indicates a systematic tracking gap.

Step 4: Check Session and Traffic Data Quality

• Compare GA4 sessions to Google Ads click count for paid search — the ratio should be 0.6-0.9 (not above 1.0 which suggests sessions inflation)
• Check Default Channel Grouping in GA4 Acquisition report — if "Unassigned" or "Direct" is disproportionately large, UTM parameters may be missing on your paid traffic
• Look for unexpected referrals — your own domain appearing as a referrer suggests missing cross-domain tracking or payment processor referral exclusion

Step 5: Verify Data Retention and BigQuery Export

• Admin then Data Settings then Data Retention — confirm it is set to 14 months (not 2 months default)
• Admin then BigQuery Links — confirm export is active if you need raw event data
• In Explorations, try to query data from 13 months ago — if it is unavailable, your retention setting was too short and this data is permanently lost

Step 6: Validate Google Ads Link and Conversion Import

• Admin then Google Ads Links — confirm link is active
• In Google Ads: Tools then Conversions — check status of all GA4-imported conversion actions (should show "Recording" not "Inactive")
• Check for duplicate conversion actions: same event tracked via both GA4 import and Google Ads tag

Step 7: Internal Traffic Exclusion Check

Test whether your internal traffic filter is working:

1. Note your office IP address
2. Check GA4 Admin then Data Filters — confirm an Internal Traffic filter exists and is Active
3. Browse several pages from your office network and verify in Realtime that the sessions do not appear

Summary

A thorough GA4 audit covers tag integrity, duplicate prevention, conversion validation, traffic quality, data retention, Google Ads link, and internal traffic filtering. Most properties fail at least 3 of these checks. Fixing them produces cleaner data, better attribution, and more accurate Smart Bidding signals.

See our GA4 Setup & Audit service for a professional property audit.

Want a professional GA4 audit? Contact Adslytics.