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CO-304 Denial Code: Submit to Patient's Hearing Plan

CO-304 means the patient's medical plan has no benefit for these services, typically hearing aids or related hearing services, and wants you to submit them to the patient's separate hearing plan. The claim wasn't forwarded, so you must rebill.

Quick facts

Code
CO-304 (CARC 304)
Status
Active In use since March 1, 2022.
Code set
Claim Adjustment Reason Codes (CARC)
Group codes
  • CO (Contractual Obligation): The usual group. The medical plan pays nothing; the provider rebills the hearing plan and doesn't bill the patient yet.
  • PR (Patient Responsibility): Sometimes used when the payer considers the patient responsible for pursuing the hearing benefit. Confirm the hearing plan's decision first.
Official description
Claim received by the medical plan, but benefits not available under this plan. Submit these services to the patient's hearing plan for further consideration.
X12 Claim Adjustment Reason Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What CO-304 means

CARC 304 says the claim was received by the medical plan, but benefits are not available under this plan; submit these services to the patient’s hearing plan. The medical payer is directing you to a separate hearing benefit and is not forwarding the claim itself.

Hearing benefits are commonly offered as a separate program, especially for hearing aids. They may be run by a specialized hearing benefit administrator with its own network, pricing, and required forms. A medical plan that carves hearing aids out will use CO-304 when those items land on a medical claim.

The forwarded version is CO-305. With CO-304, the claim stays unpaid until you send it to the hearing plan.

Example: an audiology practice fits a pair of hearing aids and bills the patient’s medical plan with HCPCS hearing aid codes. The medical plan excludes hearing aids but the employer offers a hearing program through an administrator. The remittance returns CO-304, and the practice must submit to that administrator, which may require its own authorization.

Common causes

  • Hearing aids and fittings billed to medical coverage that excludes them.
  • Separate hearing benefit not identified at intake.
  • Practice not in the hearing administrator’s network, so staff defaulted to the medical plan.
  • Routine hearing screenings that the medical plan treats as part of the hearing benefit.

How to fix it

  1. Identify the hearing plan and verify eligibility, benefit amounts, and frequency limits for devices.
  2. Check authorization or order requirements with the hearing administrator.
  3. Submit a new claim to the hearing plan in its required format.
  4. Keep diagnostic testing with the medical plan when it was ordered for a medical reason and the medical plan covers it.
  5. Bill the patient for any balance the hearing plan assigns, following your written agreement.

How to prevent it

  • Verify hearing benefits before ordering devices, not only medical coverage.
  • Separate device and diagnostic services so each goes to the right plan.
  • Join the hearing administrators’ networks used by your patients’ plans.
  • Give written estimates for devices before fitting.

Specialty notes

Audiology practices, ENT groups with audiology services, and hearing aid dispensers see CO-304. Medicare traditionally doesn’t cover hearing aids, while many Medicare Advantage plans offer hearing benefits through separate administrators, which is a frequent source of this code.

Remark codes that may appear with CO-304

  • N130 (Consult plan benefit documents/guidelines for information about restrictions for this service.): Points to medical plan documents that exclude hearing aids or assign them to a separate benefit.
  • CO-305 (Claim received by the medical plan, but benefits not available under this plan.): Same routing, but the medical plan forwarded the claim to the hearing plan for you.
  • 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.
  • PR-204 (This service/equipment/drug is not covered under the patient's current benefit plan): Service not covered under the current benefit plan, with no alternative plan named.
  • CO-109 (Claim/service not covered by this payer/contractor.): Not covered by this payer; send to the correct payer.

CO-304 FAQ

Which services lead to CO-304?

Usually hearing aids, hearing aid fittings and follow-up, batteries, and sometimes routine hearing exams, billed to a medical plan whose employer or plan sponsor offers a separate hearing benefit.

Are diagnostic hearing tests part of the hearing plan?

Often not. Diagnostic audiology testing ordered for a medical reason is frequently covered by the medical plan, while hearing aids and routine screenings go to the hearing benefit. Plans differ, so verify both.

How do I find the hearing plan?

Ask the patient, check the member materials or card, or ask the medical plan which company administers hearing benefits. Many hearing benefits are managed by specialized administrators with their own provider networks.

Can I bill the patient for the hearing aid?

After the hearing plan processes the claim, the patient owes whatever it assigns as patient responsibility plus any agreed amounts above the benefit. If there's no hearing plan, follow your financial agreement with the patient.