Behavioral Health Billing Denials: Causes, CARCs and Prevention (2026)

Most behavioral health denials trace back to a handful of fixable causes: eligibility and carve-out errors, missing authorization, weak medical necessity documentation, time-code mismatches, diagnosis problems and provider enrollment gaps.

Therapy and counseling practices bill high volumes of similar, low-dollar, time-based claims. One broken step, such as a benefit that is managed by a separate behavioral health company or a clinician who is not yet enrolled with a plan, can deny every session for weeks before anyone notices.

The good news is that the remittance tells you where the break is. Each denial carries a Claim Adjustment Reason Code (CARC) and often a Remittance Advice Remark Code (RARC). Read them in a consistent way, map each one to the person who owns that step, and the same denial stops coming back.

This guide covers the denial causes therapy and behavioral health practices see most often, the CARC each one usually produces, how to fix the claim in front of you and how to prevent the next one. Psychiatrists and PMHNPs billing E/M with psychotherapy, TMS or esketamine should also read our psychiatry denial management guide.

The Most Common Behavioral Health Denials at a Glance

The CARC wording below comes from the X12 code list. Payers choose which code to apply, so always read the RARC and the payer’s notes as well.

1. Eligibility, Benefits and Carve-Out Errors

Mental health benefits often differ from the medical plan. Some employers and health plans contract a separate behavioral health organization to manage them, so the card in your hand may not name the company that actually pays therapy claims. Sending the claim to the medical carrier then produces a CO-109 denial.

Check, before the first session and again when the plan year changes:

• Active coverage on the date of service, and whether another plan is primary.
• Who administers outpatient behavioral health benefits, and their claims address or payer ID.
• In-network status for the specific clinician, not just the practice.
• Copay, coinsurance and deductible for outpatient mental health visits.
• Annual visit limits, authorization rules and any limits on telehealth.

Our eligibility verification team runs these checks before each visit so coverage problems surface before the claim, not after it.

2. Missing or Expired Authorization (CARC 197)

Plans differ widely. Some require authorization for routine outpatient therapy after a set number of visits; many require it for higher levels of care such as intensive outpatient or partial hospitalization programs, psychological testing or some specialized therapies. Traditional Medicare does not use prior authorization for routine outpatient psychotherapy, but Medicare Advantage and Medicaid managed care plans may.

Authorization denials usually come from three gaps: nobody checked, the authorization expired or ran out of visits, or the claim did not carry the authorization number. Track approved visit counts and end dates for every patient, and alert the clinician before the last approved session. If a service was urgent and the plan allows it, see our guide to retro authorization.

3. Medical Necessity Denials (CARC 50)

A medical necessity denial means the payer did not see enough in the record to justify the service, its frequency or its length. In therapy, this usually shows up on long-term weekly care, on 60-minute sessions billed every week, or when notes read the same from visit to visit.

Documentation that supports medical necessity usually includes the diagnosis and the symptoms behind it, functional impairment, a treatment plan with measurable goals, the interventions used in each session, the patient’s response and the reason continued care is needed. Standard formats such as SOAP or DAP notes help, as long as each note is specific to that session.

Parity matters. Under the federal Mental Health Parity and Addiction Equity Act, group health plans and insurers that cover mental health benefits cannot apply limits to them that are more restrictive than those for medical and surgical benefits. Plans must also make their medical necessity criteria available on request. Ask for the criteria in writing before you appeal.

4. Diagnosis Problems (CARC 11 and 167)

Diagnosis denials fall into two groups. CARC 11 means the payer considers the diagnosis inconsistent with the service. CARC 167 means the diagnosis is not covered under the plan or policy.

A common trigger is billing psychotherapy with only a Z code, such as a code for relationship distress or a life stressor. Z codes are valid ICD-10-CM codes and add useful context, but many payers will not pay psychotherapy when a Z code is the only or primary diagnosis. Medicare contractors publish the diagnoses that support psychotherapy in their local coverage articles. Code the clinical diagnosis the clinician actually documented, to the highest specificity, and list Z codes as secondary when they apply. Our mental health ICD-10 code guide covers diagnosis selection in depth.

5. Time and Code Selection Errors

Psychotherapy codes are time-based. Medicare contractor guidance, such as First Coast’s billing article for psychiatric services, follows the CPT time thresholds below and states that sessions under 16 minutes are not reported. The note must show the actual psychotherapy time or start and stop times.

CPT also instructs that 90785 is not reported with the crisis codes 90839 and 90840, and that the crisis codes are not reported with 90832 to 90838 for the same session. Family (90846, 90847) and group (90853) codes have their own rules. For the full code set and examples of each session type, see our mental health CPT codes guide and how to bill a therapy session.

Telehealth adds another layer: place of service and modifier rules differ between Medicare, Medicaid and commercial plans. Our telehealth mental health billing guide explains the current rules.

6. Provider Enrollment and Credentialing Gaps (B7, 170, 185)

When a clinician is not enrolled, credentialed or linked to the right group with the payer on the date of service, the claim denies regardless of how good the documentation is. Typical codes are B7 (provider not certified or eligible on this date of service), 170 (denied when performed by this type of provider) and 185 (rendering provider not eligible to perform the service).

Behavioral health has extra variables: licensed associates under supervision, payer rules about which license types can bill, and Medicare. Since 1 January 2024, marriage and family therapists and mental health counselors can enroll in Medicare and bill for their services, but only after their enrollment is approved. Confirm effective dates before a new clinician sees patients. Our mental health credentialing guide walks through the process.

7. Data, Filing and Duplicate Errors (CARC 16, 29, 18)

These are the most preventable denials. CARC 16 always comes with a remark code that names the missing or invalid item, such as a subscriber ID, rendering NPI or authorization number. CARC 29 means the claim reached the payer after its filing limit; Medicare’s limit is 12 months from the date of service, while commercial and Medicaid limits are set by contract or state rules and can be much shorter. CARC 18 flags an exact duplicate, which often happens when staff resubmit instead of checking claim status. See our guides to CO-16 and CO-29 for the fixes.

Worked Example: A Therapy Claim Denied for Authorization

A hypothetical LPC sees an established patient for a 55-minute session and bills 90837 with F33.1 (major depressive disorder, recurrent, moderate). The remittance shows CO-197.

1. Read the codes. CARC 197 means authorization was absent. The RARC and payer notes confirm the plan requires authorization after the initial visits.
2. Check the record. The authorization log shows 12 visits approved; this was visit 13. The authorization had run out.
3. Decide the path. Call the plan or check its portal to see whether it accepts a retroactive request. If it does, submit the request with the treatment plan and recent notes, then resubmit the claim with the new number.
4. Prevent the repeat. Add an alert at visit 10 of 12 so the clinician can request a concurrent review before the visits run out.

What to Do When a Denial Arrives

Appeal deadlines vary. For traditional Medicare, a redetermination must be requested within 120 days of receiving the initial determination. Commercial and Medicaid deadlines are set by the plan and state, so record them for each payer. Our medical claim appeal guide explains each level.

A Denial Prevention Checklist for Therapy Practices

• Verify benefits, carve-out administrator and in-network status before the first visit and at each plan-year change.
• Log authorizations with visit counts, end dates and the number to put on the claim.
• Record psychotherapy time or start and stop times in every note.
• Code the documented clinical diagnosis to full specificity; use Z codes as secondary where they apply.
• Confirm each clinician’s enrollment effective date with every payer before scheduling.
• Scrub claims for missing IDs, NPIs and authorization numbers before submission.
• Check claim status before resubmitting, to avoid duplicates.
• Track denials by CARC, payer and clinician monthly, and fix the root cause.

Denial rate is one of several warning signs of lost revenue. See signs your mental health billing is losing revenue for the KPIs to watch, and the mental health billing guide for the full billing workflow.

Frequently Asked Questions