CPT Code 90791: The Psychiatric Diagnostic Evaluation Billing Guide

The intake code every independent therapist uses — how to bill it, document it, and avoid the most common denial.

CPT code 90791 is used to bill for the psychiatric diagnostic evaluation performed by a non-medical mental health professional. For LCSWs, LPCs, LMFTs, and psychologists, 90791 is the intake code — the first billable encounter with a new patient. It is the evaluation that establishes the diagnosis, builds the initial treatment plan, and opens the door to ongoing psychotherapy billing.

Most denials on 90791 come from a handful of predictable documentation or frequency issues. This guide walks through what 90791 actually covers, what documentation Medicare expects, and how to bill it correctly.

What 90791 covers

The CPT description for 90791 is “Psychiatric diagnostic evaluation.” It is distinct from 90792, which is the same evaluation performed by a medical provider who can also conduct a medical assessment and prescribe. 90791 is the code non-medical mental health professionals use for the diagnostic intake.

A complete 90791 evaluation generally includes:

• A comprehensive biopsychosocial history (presenting problem, history of present illness, past psychiatric history, substance use history, medical history, family history, social and developmental history)
• Mental status examination
• A DSM-5-TR diagnosis or working diagnosis with specifiers
• A preliminary treatment plan with goals, frequency, modality, and estimated duration
• A clinical recommendation (ongoing individual therapy, couples or family therapy, higher level of care, referral for medication evaluation, etc.)

How often 90791 can be billed

Medicare generally allows 90791 once per client per provider per episode of care. A second 90791 for the same patient by the same provider within a year is frequently denied unless there has been a clinically significant change — a new presenting problem, a return to treatment after a significant gap, or a new clinical evaluation warranting a formal re-assessment.

If the patient has been seen by another provider in your practice, you may be able to bill 90791 as the establishing provider for your relationship, but payer policies vary. Commercial payers often apply a 12-month lookback and deny a second 90791 within that window.

Documentation that holds up

A defensible 90791 note should include all of the elements Medicare and most commercial payers expect from a psychiatric diagnostic evaluation:

• Date of service and total time spent in the evaluation (even though 90791 is not time-based, time is still worth documenting)
• Chief complaint and history of present illness
• Past psychiatric history, including prior diagnoses, hospitalizations, and treatment
• Substance use history
• Medical history and current medications
• Family psychiatric history
• Social and developmental history
• Mental status exam
• Diagnosis with ICD-10 codes
• Treatment plan with specific goals, therapy modality, frequency, and duration
• Disposition and recommendations

The mental status exam is one of the most frequently missing elements in 90791 denials. A complete MSE is not optional for a psychiatric diagnostic evaluation — its absence is a documentation gap that can void the claim.

90791 reimbursement

Medicare reimburses 90791 at a rate higher than any of the individual psychotherapy codes, reflecting the broader scope of the diagnostic evaluation. The specific rate varies by locality and changes annually with the Medicare Physician Fee Schedule. LCSWs, LPCs, and LMFTs all receive the same reimbursement rate for 90791 under current Medicare parity rules.

Commercial rates vary. Some payers reimburse 90791 substantially higher than the ongoing psychotherapy codes; others use a flat multiplier.

Common 90791 denials

Frequency denial

A second 90791 for the same patient within the payer’s lookback window will be denied. If a genuine re-evaluation is warranted, your note must explicitly document the clinical reasons — a new presenting problem, return after a significant gap in care, or changed clinical circumstances justifying a formal re-assessment.

Missing mental status exam

Notes without a complete mental status examination are a common denial for 90791 on documentation review. The MSE should address appearance, behavior, mood, affect, speech, thought process, thought content, perception, cognition, insight, and judgment.

Insufficient history

If the evaluation note reads more like a brief initial session than a comprehensive diagnostic workup, the payer may determine that a psychiatric diagnostic evaluation was not actually performed and that 90834 or 90832 would have been more appropriate.

Missing diagnosis or treatment plan

90791 is an evaluation code — it must conclude with a diagnostic impression and a treatment plan. Notes that stop short of a formal diagnosis or that do not propose a plan will fail documentation review.

Billing 90791 with other codes

You generally cannot bill 90791 and a psychotherapy code (90832, 90834, 90837) for the same patient on the same date of service, because the diagnostic evaluation is considered a distinct service that includes any therapeutic engagement provided during the evaluation.

You also cannot bill 90791 and 90792 on the same date of service by different providers in the same practice for the same patient — Medicare considers these mutually exclusive.