All "employees" are paid users.
Also all "freelancers" who
- don't have "restricted access" (more inormation on this matter here) and who
- aren't registered as employees in another account
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.