With private health insurance, billing follows the German fee schedule for psychotherapists (GOP). For the individual services, the GOP refers to the fee schedule for physicians (GOÄ). You receive an invoice each month and submit it to your insurer.
Most insurers cover psychotherapy, but not all to the same extent. Some cap the number of sessions, some require approval in advance. So ask your insurer in writing, before you start, what it covers.
If you are entitled to Beihilfe, psychotherapy is eligible for it, but it has to be approved before treatment begins. You apply for that prior approval to your Beihilfe office, usually after the trial sessions. I prepare the paperwork for it together with you.
Cognitive behavioural therapy (Verhaltenstherapie) is normally approved for 60 individual sessions, and in exceptional cases for a further 20. Worth knowing: short-term and acute treatment count towards those 60 sessions; they are not in addition.
The share Beihilfe does not cover is met by your private supplementary insurance. For places in the group we clarify eligibility for Beihilfe in advance, case by case, because the rules differ from one Beihilfe office to the next.