I have raised my hourly rate to make up for the extras. Good luck with your case. What is billed depends on the nature of the funding source. Some systems indicate that the documentation time has already been factored into the rate which is based on direct service time with the client. Generally funding sources do not consider direct payment for this function although it can sometimes be considered part of the treatment or evaluation session.
Billing is done according to the funding source.
Some require units by CPT code. Home Health requires billing by visit. The degree of supervision is dictated by the AOTA Standards of Practice, Supervision Guidelines and the Licensure Law within the State where the therapist is practicing. In the State in which I practice, the OT assumes responsibility for the actions of the OTA and therefore sets the frequency and type of supervision. The OT is not generally required to be physically present but is usually available by pager or telephone.