GA4 honestly shows what you send it. The problem is what usually gets sent. Here are the ten mistakes I find most often in audits — each one distorts the data behind your budget decisions.
Setup mistakes
- Duplicate transactions: the purchase fires from the site, the server, and again on “thank you” page refresh. Reported revenue is 1.5× reality.
- No internal traffic filter: your team and contractors click conversions in.
- Referral exclusions not set: the payment gateway becomes the purchase “source”.
- No cross-domain between site and landing pages: one session becomes two.
- Default property time zone and currency: you compare days that never existed.
Interpretation mistakes
- Comparing GA4 sessions with Universal Analytics: different methodologies — the “traffic drop” is an illusion.
- Last-click attribution decisions on long sales cycles.
- Engagement rate mistaken for the old bounce rate.
- Privacy thresholds and sampling ignored: numbers “dance” and you blame the ads.
- Micro-conversions (scroll, phone click) mixed with macro (lead, purchase) — “plenty of conversions, no money”.
What to do
Run your analytics through a checklist quarterly: a test purchase, revenue reconciliation with the CRM, source check on the last 20 deals. One hour of work — and decisions rest on reality again. I can check your setup — it’s a quick audit.