for psychotherapy add ons (including 90833) medicare requires you EITHER document total time OR start/stop time, not both. Some commercial insurances require start/stop times. Depends on the plan.
E&M codes (including 99205) only require total time, not start/stop times. Some plans do require start/stop times for whole visit if you are using psychotherapy add on codes. For 99205 if billing on time, you can include time on non-face-to-face activities including reviewing charts (other charts from different specialty or clinic, not your own records or those of your practice), documentation, coordination of care (e.g. collateral). If you bill on time, then you cant use these codes with a psychotherapy add on.
Not sure if you were asking about this, but with the 2021 changes, it is very hard to bill 99205 on MDM and thus rare that you would be able to bill 99205 with a therapy add on. Patients basically have to need hospitalization, lots of record review and collateral with independent review of records, and/or prescribing lithium or clozapine to an acutely decompensated pt. But if you bill on time you can easily use 99205 if you spend 60mins on a new pt visit.