If you're a therapist handling your own billing, two codes will show up constantly: 90791 and 90837. Understanding the difference — and getting them right — has a direct impact on how quickly and accurately you get paid.
90791 — Psychiatric Diagnostic Evaluation
This code is used for the initial intake assessment, typically the first session with a new client. It covers a comprehensive evaluation of the patient's history, presenting concerns, and initial treatment plan. It's billed once per client at the start of treatment (and occasionally again if there's a significant gap in care or a major change in clinical presentation).
90837 — Psychotherapy, 60 Minutes
This is the standard code for an individual therapy session lasting 53 minutes or more. It's the most commonly billed code for ongoing weekly therapy. Its shorter sibling, 90834, covers sessions between 38 and 52 minutes — payers often reimburse 90837 at a meaningfully higher rate, so accurate session-length documentation matters.
Why getting this right matters
Billing 90837 for a 30-minute session — or 90791 for a routine follow-up — can trigger documentation requests, audits, or denials. Consistent, accurate use of these codes (backed by session notes that support the time billed) keeps claims clean and protects your practice if a payer ever requests records.
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