90837 vs. 90834: Which Code Should You Bill?

The most common billing decision in outpatient therapy — and the compliance question auditors most often ask.

The choice between CPT codes 90837 and 90834 is the single most frequent billing decision in outpatient mental health practice. Both codes describe individual psychotherapy. Both apply to the same patient populations and diagnoses. What separates them is a single factor: session length.

Getting this choice right matters for two reasons. First, the correct code is determined by the actual length of the session, and consistently mismatching code to session length is a documentation audit risk. Second, high-frequency 90837 billing has been specifically identified as an audit flag by Medicare contractors and the OIG, making the 90837-vs-90834 decision one of the most compliance-sensitive choices therapists make.

The simple rule

That is the entire rule. If your session ran 52 minutes or less, you bill 90834. If it ran 53 minutes or more, you bill 90837. Code selection follows actual session length, not your standard appointment block, not the code you typically use, and not the code that reimburses better.

Why this decision matters for audit risk

Medicare contractors and the OIG have identified high-frequency 90837 billing as a utilization concern. Therapists who bill 90837 for a high percentage of sessions — often cited as over 80 percent — have been selected for post-payment documentation review more often than therapists with a more varied code distribution.

This does not mean you should downcode from 90837 to 90834 to reduce audit risk. Downcoding is its own compliance problem and misrepresents the services provided. What the pattern data suggests is simpler: your code selection should follow your actual session lengths, and your session lengths are probably more varied than you think.

Sessions do not all run exactly the same length. Some end early because the clinical work concluded. Some run long because of clinical complexity. Some are scheduled as shorter check-ins. A billing profile that reflects real variation in session length is more defensible than one that uses a single code for nearly every encounter.

The appointment block question

Many therapists schedule in 45- or 50-minute blocks. A 50-minute therapy hour, consistently delivered, falls squarely within the 90834 range (38–52 minutes). Billing 90837 for those sessions requires that they actually run 53 minutes or longer — not that they are scheduled for 50 minutes and sometimes run a few minutes over.

If your standard block is 50 minutes, 90834 is likely your most appropriate primary code. If your standard block is 60 minutes and sessions consistently run the full block, 90837 is appropriate. The key is that the code reflects the actual length of the session, and your documentation reflects the same.

The documentation test

The question to ask of every session note is: if an auditor read this note cold, could they verify the time I billed?

A note that documents “session 10:00–10:55, total 55 minutes” supports 90837. A note that documents “60-minute session” without start/stop time does not, because the auditor cannot verify the 53-minute minimum was met.

The same standard applies to 90834. A note that documents “session 2:00–2:47, total 47 minutes” clearly supports 90834. A note that lists only “therapy session” with no time detail leaves the claim unsupported.

What happens on audit

If a Medicare contractor selects a sample of your 90837 claims for documentation review, the review typically examines:

• Whether the session note documents time sufficient to support 90837
• Whether the diagnosis supports the medical necessity of a 60-minute session
• Whether the therapeutic content is consistent with an extended psychotherapy session
• Whether the treatment plan reflects ongoing clinical need for 60-minute sessions

Claims where the documentation does not support the time billed are typically recouped — the payment is reversed and the therapist is billed for the overpayment. Patterns of unsupported 90837 claims can lead to extrapolated repayment demands (where a small sample’s error rate is projected across all claims in a period) and in rare cases to referral for further action.

When 90837 is clinically appropriate

90837 is the right code when the session genuinely runs 53 minutes or longer of psychotherapy. Clinical situations where 60-minute sessions are commonly appropriate include:

• Trauma-focused therapies with extended exposure or processing work (EMDR reprocessing phases, prolonged exposure sessions)
• Complex presentations requiring significant time for assessment and intervention within each session
• Patients whose clinical profile (severe symptoms, cognitive complexity, interpersonal complications) warrants longer contact
• Structured therapy protocols that specify 60-minute sessions

When 90837 is clinically indicated and the documentation supports it, billing 90837 is entirely appropriate. The audit concern is specifically about the pattern of using 90837 as an undifferentiated default.

When 90834 is clinically appropriate

90834 is the right code when the session runs 38 to 52 minutes of psychotherapy. This fits:

• A standard 45- or 50-minute therapy hour
• Sessions in which the clinical work concluded before a full 60 minutes was needed
• Therapy protocols with shorter standard session lengths
• Sessions with patients who cannot tolerate longer therapeutic contact

The bottom line

The 90837 vs. 90834 decision is simple in principle and compliance-sensitive in practice. Let the session length drive the code selection. Document the time. Ensure your diagnosis and treatment plan support the length billed. And expect that a billing profile reflecting a mix of 90832, 90834, and 90837 — proportional to your actual clinical work — will serve your practice better than one that uses 90837 as the default.