CPT 90791: The Psychiatric Diagnostic Evaluation Code for Therapists
Outline
CPT 90791 is the code most non-prescribing therapists reach for on the first appointment with a new client. It is the psychiatric diagnostic evaluation code, and it covers the comprehensive intake assessment that establishes a diagnosis and a treatment plan before ongoing psychotherapy begins. Psychologists, licensed clinical social workers, licensed professional counselors, and marriage and family therapists all bill it for that first visit, which makes it one of the highest-volume codes in outpatient mental health.
Two things about the code trip clinicians up. It is not time-based, so there is no time band to hit and no level to select the way an Evaluation and Management code works. And it carries no medical services, which is the line that separates it from 90792 and from the E/M codes a prescriber uses. This guide covers what the evaluation actually includes, who bills it, how to document a defensible note, the frequency limits payers apply, telehealth rules, and the diagnoses most often paired with it. For how the diagnostic codes sit on the same claim with the ICD-10 codes the evaluation produces, see the ICD-10 codes for therapists hub.
Educational reference for licensed US therapists, psychologists, counselors, and clinical social workers. CPT descriptors and payer coverage vary by payer and state; verify current rules against the AMA CPT guidance and the CMS Physician Fee Schedule lookup before billing.
What CPT 90791 actually is
It is the Current Procedural Terminology code for a psychiatric diagnostic evaluation without medical services. The code sits in the psychiatry section of the AMA CPT codebook and describes an integrated biopsychosocial assessment: the clinical interview, a history, a mental status examination, and the formulation that produces a diagnostic impression and treatment recommendations. It is the gateway code, the one that opens an episode of care before the per-session psychotherapy codes take over.
The descriptor has no time component. Unlike the timed psychotherapy codes, where the clock decides between 90832, 90834, and 90837, the diagnostic evaluation is billed once for the assessment regardless of whether it runs fifty minutes or ninety. Most payers expect the evaluation to take roughly an hour in practice, and a note that documents a ten-minute encounter under this code will not survive review, but the code itself is defined by the service delivered rather than the minutes spent.
The other defining feature is the absence of medical services. The evaluation does not include a physical examination, prescription decisions, or the ordering of labs. The moment those medical elements enter the visit, the correct code shifts to 90792 or to an E/M code, depending on the clinician’s licensure. For a non-prescribing therapist that boundary is rarely a question, because the scope of practice already excludes medical services.
What the diagnostic evaluation includes
The diagnostic evaluation is a defined clinical service, not an open-ended first session. A complete evaluation under this code works through a consistent set of domains, and the note has to show that the work was done.
- Presenting concern and history of the problem in the client’s own words, with onset, course, and the events that prompted the referral.
- Relevant psychosocial and developmental history: family, relationships, education, occupational functioning, substance use, prior treatment, and any trauma history the client is ready to disclose.
- A mental status examination covering appearance, behaviour, mood and affect, thought process and content, cognition, insight, and judgement.
- A risk assessment addressing suicide, self-harm, harm to others, and child or elder safety where relevant.
- A diagnostic impression with the specific ICD-10-CM code that the formulation supports.
- Treatment recommendations, including the proposed modality, frequency, and the per-session code the ongoing work will use.
That last element is where the evaluation connects to the rest of the chart. Once the intake is complete and weekly therapy begins, the per-session code is usually 90834 for a 45-minute session or 90837 for a 60-minute session. The diagnostic evaluation establishes the diagnosis those later sessions treat.
90791 vs 90792 vs 99204: who bills which
The choice between the three new-patient evaluation codes comes down to licensure and whether medical services were part of the visit, not to how long the session ran or how complex the client is.
| Code | Who bills it | Medical services | Documentation focus |
|---|---|---|---|
| 90791 | Psychotherapists (no prescribing) | No | Diagnostic impression, MSE, treatment plan |
| 90792 | Prescribers (psychiatrists, PMHNPs) | Yes | All of the above plus medical history and prescription decisions |
| 99204 | Prescribers (E/M framework) | Yes | E/M-format note: history, exam, moderate MDM or 45–59 min |
For a non-prescribing licensed therapist, the new-patient evaluation code is almost always 90791. A prescriber on staff chooses between 90792 and 99204 based on payer preference and how the visit is structured; some payers prefer the psychiatric evaluation code for the first visit while others reimburse the E/M code at a higher rate. The full comparison of the E/M pathway lives in the 99204 new patient evaluation guide.
The practical rule for a mixed practice is simple. Map each clinician’s licensure to the code family before the intake: the LCSW or LPC produces a diagnostic evaluation note, the psychiatric nurse practitioner produces a 90792 or 99204 note. Billing the diagnostic evaluation code for a visit that actually involved medical services, or billing an E/M code from a non-prescribing license, are the two errors a payer audit catches first.
How to document a defensible evaluation note
A reviewer reading a diagnostic evaluation chart is checking for two things: that a genuine comprehensive assessment took place, and that the diagnosis is supported by the content rather than dropped in at the end. The note earns the code by working through the domains above and tying them to a specific diagnostic conclusion.
The mental status examination is the section payers and board reviewers read most closely on this code. A generic line such as “MSE within normal limits” weakens the note. Reviewers expect to see actual descriptors across each MSE domain (appearance, behaviour, mood and affect, thought process and content, cognition, insight, judgement) with at least a phrase of clinical observation behind each.
The diagnostic impression should pair the clinical formulation with a specific ICD-10-CM code, not a placeholder or a “rule out” diagnosis carried indefinitely. If the presentation genuinely does not yet meet full criteria, an adjustment-disorder or unspecified code that the documentation supports is more defensible than a provisional label with nothing behind it. The treatment recommendations then close the loop by naming the modality, the planned frequency, and the per-session code the episode will use.
A defensible evaluation note therefore contains the date of service, the presenting concern, the psychosocial history, the full MSE, an explicit risk assessment, the diagnostic impression with its ICD-10-CM code, the treatment plan, and the clinician’s signature and credentials. The risk assessment in particular is not optional: its absence is one of the most common reasons a diagnostic evaluation note fails a board or payer review. A structured suicide risk assessment template keeps that section consistent across the intake and the progress notes that follow.
How often you can bill 90791
The diagnostic evaluation is an episode-opening service, so payers limit how often it can be billed. The common rule is once per client per provider per year, on the theory that a single comprehensive evaluation opens the episode and the per-session codes carry the work from there. The exact frequency rule varies by payer, and some state Medicaid programs apply tighter limits than commercial plans.
A second evaluation is appropriate, and usually reimbursable, in a few situations. A client who returns after a long gap in treatment may need a fresh diagnostic evaluation rather than resuming on the old formulation. A client who develops a distinctly new condition can warrant a new assessment. And some payers permit a single complex intake to be split across two sessions, billed as two units of the code, when the clinical complexity genuinely requires it and prior authorisation is in place.
Two billing errors recur here. The first is billing the diagnostic evaluation and an individual psychotherapy code for the same encounter on the same day; most payers will not reimburse both because the evaluation already accounts for the clinical time. The second is repeating the evaluation at the start of every authorisation period out of habit rather than clinical need. Bill the code when a genuine new evaluation takes place, document why, and the claim holds.
Telehealth and the diagnostic evaluation
The psychiatric diagnostic evaluation is on the Medicare list of services that can be delivered by telehealth, and most commercial payers reimburse a video evaluation on the same terms as an in-person one. The clinical substance does not change: a telehealth intake still works through the full set of domains, still requires a mental status examination adapted to the video format, and still carries the same risk-assessment expectations.
The differences are administrative. The claim needs the correct place-of-service code and, for many commercial payers, a telehealth modifier such as 95. Conducting a thorough risk assessment over video also calls for a confirmed client location and a safety plan that accounts for the clinician not being physically present. Place-of-service and modifier requirements shift periodically and vary by payer and state, so confirm the current rule with the specific payer before submitting telehealth claims rather than carrying last year’s setup forward.
Common diagnoses paired with the evaluation
The diagnostic evaluation is a service code; it carries no diagnosis on its own. The claim pairs it with the ICD-10-CM code the evaluation establishes. The codes below are among the most common conclusions of a new-patient intake in outpatient mental health.
- F43.23 Adjustment disorder with mixed anxiety and depressed mood, common when symptoms follow an identifiable stressor and do not meet full criteria for a primary mood or anxiety disorder.
- F41.1 Generalized anxiety disorder.
- F32.9 Major depressive disorder, single episode, unspecified.
- F43.10 Post-traumatic stress disorder, unspecified.
- F90.x Attention-deficit hyperactivity disorder, where the specifier digit indicates the presentation.
Pair the ICD-10-CM code with the CPT code on the claim: the diagnosis substantiates medical necessity and the procedure code identifies the service rendered.
How Emosapien handles the diagnostic evaluation
During a new-patient intake, Emosapien’s Scribe Agent works alongside the clinician as an active in-session partner rather than passive transcription. It maps the clinician’s licensure to the right code family before the session starts, so a non-prescribing therapist’s intake produces a diagnostic evaluation note while a prescriber’s intake produces a 90792 or 99204 note. It structures the evaluation across the diagnostic domains, flags a missing risk assessment or an empty MSE section before the note is signed, and pre-populates the diagnostic impression with the matched ICD-10-CM code from the formulation.
The clinician reviews and signs; the agent handles the structural plumbing that makes the chart defensible. For a practice where intake documentation is the part of the week that runs late, that means the evaluation note leaves the session with its required elements already on the page.
See how the Scribe Agent fits into an intake workflow on the AI clinical notes page, or create a free clinician account to run your next diagnostic evaluation through Emosapien.