All "employees" are paid users.
Also all "freelancers" who
- have "restricted access" de-activated and
- aren't registered as employees in another account
- have comprehensive access to other groups
are paid users.
The restricted access is activated automatically when adding a new freelancer so he is fundamentally non paid. When that status is deactivated the user will be a paid user.
If you want to get an overview of your paid and non paid users you can download the user list in the admin section as a csv-file or xlsx-file via the icon above the user list.