CPT 90791
Psychiatric Diagnostic Evaluation
How it is billed
- Reported without medical services; where an evaluation includes a medical assessment and prescribing, the companion code covering medical services applies instead
- Not time-based — the code describes a service rather than an interval, so no time threshold has to be met and none should be reported as if it were
- Most payers permit one per patient per provider per episode of care, and many define that operationally as once per calendar year
- Where a second clinician in the same group evaluates the same patient in the same period, the claim frequently duplicates against the first and needs the distinct provider and clinical rationale to survive
- The interactive complexity add-on applies where communication factors — a third party, a translator, a young child — genuinely complicate the evaluation, and is reported alongside rather than instead
What the record must show
- The elements of the evaluation should appear as an evaluation: presenting problem, relevant history, mental status examination, diagnostic formulation and the treatment plan that follows from it
- Where a re-evaluation is billed within a payer's frequency window, the note must justify why — a new episode, a substantial change in presentation, or a transfer of care
- Interactive complexity, where reported, needs its factor named; the add-on is a specific circumstance rather than a general statement that the session was difficult
A worked example
A patient is referred for anxiety and attends an intake session. The clinician takes a history, performs a mental status examination, reaches a working diagnosis and agrees a course of weekly psychotherapy. 90791 covers that encounter.
The following week the therapy begins, and every subsequent session is reported with the psychotherapy codes by duration. Billing 90791 again at session two — because the clinician was still gathering history — is the error, since the diagnostic evaluation is one service rather than a phase.
Six months later the patient returns after discharge with a different presentation. A second 90791 is defensible here, and whether it pays depends on the payer's frequency rule and on the note making the new episode explicit rather than leaving it to be inferred.
What decides payment
Behavioural health denials cluster differently from medical ones. The dominant causes are eligibility and benefit structure — carve-out plans where behavioural health is administered by a separate entity with its own authorisation rules — and frequency limits, rather than the coding of the service itself.
The distinction between the evaluation with and without medical services matters more than its subtlety suggests, because it maps onto who performed it. A prescriber's evaluation including medication assessment belongs on the medical-services code, and using the non-medical code understates the work while using it in reverse invites recoupment.
Payer authorisation practice varies widely: some require no authorisation for the evaluation but authorise a defined number of subsequent sessions, others authorise from the first contact. Verifying which applies before the intake is what prevents the entire episode being unpayable.
Denials this code attracts
Modifiers that apply
Codes billed alongside or confused with this one
Billed most in — Mental & Behavioral Health · Pediatrics · Neurology
Terms used here — Prior Authorization · Eligibility Verification · Medical Necessity · Denial
How we handle it — Eligibility Verification · Prior Authorization · Medical Coding
Primary sources
What the code-set maintainers and payers actually publish about billing 90791.
- Medicare Benefit Policy Manual (opens in a new tab)
Centers for Medicare & Medicaid Services — What Medicare covers and under what conditions, as distinct from how a claim is processed. The starting point for any coverage or medical necessity question.
- Medicare Coverage Database (LCD/NCD) (opens in a new tab)
Centers for Medicare & Medicaid Services — Searchable national and local coverage determinations. The direct answer to whether a diagnosis supports medical necessity for a given procedure.
- CPT code set (opens in a new tab)
American Medical Association — Maintainer of CPT. Annual changes to CPT are the most common cause of a sudden, unexplained rise in denials each January.
Questions about CPT 90791
The initial psychiatric diagnostic evaluation without medical services — history, mental status examination, diagnostic assessment and treatment recommendations. It is the intake code in behavioural health.
No. It describes a service rather than a duration, so there is no time threshold to meet and no time-based unit calculation. Documentation should show the elements of the evaluation rather than a start and stop time.
Most payers allow one per patient per provider per episode of care, and many enforce that as once per calendar year. A second evaluation within the window needs a documented new episode, significant change in presentation, or transfer of care.
Medical services. 90792 covers a diagnostic evaluation that includes medical assessment and prescribing, typically performed by a prescriber; 90791 covers the evaluation without them. Using the wrong one either understates the work or invites recoupment.
Find out what your denials are costing you
A free billing audit reviews your denial rate, AR aging and clean claim rate against industry benchmarks. Takes about two minutes to request. No sales pitch.
No setup fees · You pay when we collect · Pricing from 3% of net collections