Medicare doesn't just require a signed note — it requires documentation that affirmatively demonstrates medical necessity for every service billed. For therapists accustomed to commercial payer requirements, Medicare's standard can come as a surprise. Notes that have never triggered a commercial payer review can fail Medicare audit standards because they don't explicitly connect the clinical presentation to the services provided.
Here's what Medicare auditors look for in mental health session documentation, and what your notes need to contain.
Medical necessity under Medicare means that the service was reasonable and necessary for the diagnosis or treatment of illness or injury, or to improve the functioning of a malformed body member. For mental health services, this translates to a specific documentation requirement: your notes must show why this patient needed psychotherapy at this frequency, at this point in their treatment, and that the patient is making progress (or documenting why the lack of progress doesn't preclude continued treatment).
The diagnosis code alone does not establish medical necessity. A note that lists "Major Depressive Disorder, recurrent, moderate" as the diagnosis and documents the session content — without explicitly connecting them — is technically deficient by Medicare standards.
Psychotherapy codes are time-based, which means your documentation must support the specific time range billed. 90832 covers 16–37 minutes, 90834 covers 38–52 minutes, and 90837 covers 53+ minutes. Medicare requires documentation of the actual start and stop times of the psychotherapy portion of the session — not just the appointment time.
This is where many therapists create inadvertent billing errors. If your session note documents a 55-minute appointment but doesn't include the start/stop time of the therapy component, an auditor cannot verify that at least 53 minutes of psychotherapy were provided. The claim becomes unsupported.
Medicare requires an active, current treatment plan for ongoing psychotherapy services. The plan must include a diagnosis, treatment goals, frequency and duration of treatment, and planned interventions. Plans must be updated at least every 90 days — though Medicare guidelines suggest updates should reflect actual clinical status, which may require more frequent revision.
Your session notes should reference the treatment plan goals, not be written in isolation from it. An auditor reading your last six months of session notes should be able to see a coherent arc of treatment connected to documented goals.
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