Many GA4 properties were set up in a rush. Small gaps — a missing filter, a duplicated purchase event — quietly distort every report built on top.
Before tagging
- Agree which business questions analytics must answer
- List the events and parameters needed for those questions
- Write the data layer specification for developers
Property settings
- Set data retention to the maximum
- Filter internal and test traffic
- Configure cross-domain tracking and referral exclusions
Testing
Compare GA4 purchases or leads with your own system for at least two weeks. A gap of a few percent is normal; anything larger needs investigating.