90837 vs 90834: which code should you actually bill?

Last updated: October 2026 · Educational guide, not billing advice.

These two codes cover the same service — individual psychotherapy — at different session lengths. The difference sounds trivial, but 90837 is one of the most audited codes in outpatient mental health. Here's how to choose without losing sleep (or revenue).

The time rules

The ranges come from the midpoint convention most payers apply: a code is billable once you pass the midpoint between it and the shorter code. A 52-minute session is a 90834. A 53-minute session is a 90837. Document start and stop times — that one habit resolves most audit exposure.

Why 90837 gets flagged

Payers profile billing patterns. If 95% of your sessions are billed as 90837 while your peers bill mostly 90834, you become an outlier — and outliers get records requests. This doesn't mean "never bill 90837." It means: bill it when the session actually ran long and the clinical need is documented.

Medical necessity is the real test

Time gets you in the door; medical necessity keeps the payment. For 90837, your note should make it obvious why this client needed 60 minutes today — acute symptoms, crisis work, trauma processing that can't be safely truncated. Boilerplate notes are what turn a records request into a recoupment demand.

Practical rules of thumb

• Schedule honestly: if your practice model is 50-minute hours, 90834 is usually your code.
• If you bill 90837, your note should show start/stop times and a sentence of clinical justification.
• Check each payer's policy — some Medicare Advantage and Medicaid plans reimburse 90837 at rates that barely clear 90834, or require prior authorization.
• Re-verify eligibility before sessions; a denied claim for a lapsed plan wastes the note you wrote.