Why do duplicates occur even when duplicate checking is enabled?

Duplicate detection rules provide a false sense of security if you believe they prevent duplicates. They do not.

It alerts you; it doesn't block

The user receives a warning and can still choose to save. In a busy workday, many people simply click past it. If you want to prevent duplicates entirely, custom logic must be implemented.

It recognizes what it has been configured to recognize

If the rule is based on an exact name match, it will not match “Bergen Bygg AS” with “Bergen Bygg”. Rules based on organization numbers work much better for business customers.

Imports and integrations often bypass the rules

Data received through an import or integration may bypass the check, depending on how it is run. This is often the source of very large numbers of duplicates.

The check must be maintained

Rules must be published to be active, and they may be deactivated when changes are made. Check that they are actually running before relying on them.