Can I restrict employees from using Private time?

In Settings > Account you can disable Private time feature for the whole DeskTime account.

To do this, put a check in the box 'Disable private time'. When this is disabled, none of the users will be able to use Private time.

Instead of disabling it account-wide, you can restrict specific users from using the Private time instead. In this instance, go to Settings > Team Members > Edit, and disable Private time from there.