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CO-301 Denial Code: Submit to Behavioral Health Plan

CO-301 means the patient's medical plan has no benefit for these behavioral health services and wants you to submit them to the patient's separate behavioral health plan. The claim wasn't forwarded, so nothing happens until you rebill the correct plan.

Quick facts

Code
CO-301 (CARC 301)
Status
Active In use since July 1, 2019.
Code set
Claim Adjustment Reason Codes (CARC)
Group codes
  • CO (Contractual Obligation): The usual group. The provider must rebill the behavioral health plan; the patient isn't billed on this denial.
  • PR (Patient Responsibility): Occasionally used when the payer believes the patient must pursue the other plan. Confirm the behavioral health plan's decision before billing the patient.
Official description
Claim received by the Medical Plan, but benefits not available under this plan. Submit these services to the patient's Behavioral Health Plan for further consideration.
X12 Claim Adjustment Reason Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What CO-301 means

CARC 301 says the claim was received by the medical plan, but benefits are not available under this plan; submit these services to the patient’s behavioral health plan. The patient’s mental health and substance use benefits are carved out to a separate administrator, and the medical plan is telling you to send the claim there yourself.

It’s one of the most common routing codes for outpatient mental health. Unlike CO-300, where the medical plan forwards the claim, CO-301 leaves the next step entirely with you. Every day the claim sits with the wrong payer uses up the behavioral health plan’s filing window.

Example: a therapist bills a psychotherapy session to the medical plan listed on the front of the patient’s card. The employer carves out behavioral health to a separate vendor listed on the back. The medical plan returns CO-301, and the practice must submit a new claim to the vendor’s payer ID.

Common causes

  • Wrong payer ID for behavioral health services.
  • Carve-out vendor not identified at intake.
  • Plan switched behavioral health vendors at the start of a plan year.
  • Integrated care services in a medical practice billed to medical when the plan routes them to behavioral health.
  • Clinician not credentialed with the vendor, so staff defaulted to the medical plan.

How to fix it

  1. Identify the behavioral health plan and its payer ID.
  2. Verify eligibility and benefits with that plan for the date of service, including authorization rules.
  3. Submit a new claim to the behavioral health plan. It’s a new submission to a different payer, not a corrected claim to the medical plan.
  4. Obtain any required authorization, retroactively if the plan allows.
  5. Update the patient’s account so future sessions bill the right plan.
  6. Bill the patient only after the behavioral health plan’s decision, for cost-sharing it assigns.

How to prevent it

  • Verify behavioral health benefits separately before the first appointment.
  • Record the carve-out vendor as its own payer in your system.
  • Credential clinicians with the behavioral health vendors your patients use. See provider enrollment denials.
  • Monitor CO-301 by payer. An ERA Analyzer can reveal which plans repeatedly route claims elsewhere.

Specialty notes

Solo therapists and small group practices are hit hardest, because a single misrouted payer setup can affect every session for a patient. Weekly sessions can build up many CO-301 denials before anyone notices.

Remark codes that may appear with CO-301

  • N130 (Consult plan benefit documents/guidelines for information about restrictions for this service.): Points to plan documents showing behavioral health benefits are administered elsewhere.
  • CO-300 (Claim received by the Medical Plan, but benefits not available under this plan.): Same routing, but the medical plan forwarded the claim for you.
  • CO-109 (Claim/service not covered by this payer/contractor.): Not covered by this payer; send to the correct payer or contractor.
  • CO-297 (Claim received by the medical plan, but benefits not available under this plan.): The medical plan wants the claim sent to a vision plan instead.
  • CO-29 (The time limit for filing has expired.): Timely filing, a risk if rebilling to the behavioral health plan is delayed.

CO-301 FAQ

How do I find the patient's behavioral health plan?

Check the back of the insurance card for a mental health or behavioral health phone number, ask the medical plan, or look at the eligibility response for a carve-out vendor. The patient's HR department can also tell you.

Does the timely filing clock restart when I rebill?

Generally no. The behavioral health plan applies its own filing limit, usually from the date of service. Keep the CO-301 remittance in case you need to show the claim was filed promptly elsewhere.

Do I need a separate authorization?

Often, yes. Behavioral health vendors commonly have their own authorization or registration rules, especially for higher levels of care and some testing services. Outpatient therapy rules vary by plan.

Why does this keep happening for the same patient?

The patient's account likely still points to the medical plan. Add the behavioral health vendor as the payer for behavioral health visits so future claims route correctly.