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M37 Remark Code: Not Covered Under Age 35

M37 means the payer denied the service because the patient was younger than 35 on the date of service, and the benefit only applies at or above that age.

Quick facts

Code
M37 (RARC M37)
Status
Active In use since January 1, 1997; last modified March 8, 2011.
Code set
Remittance Advice Remark Codes (RARC)
Group codes
  • CO (Contractual Obligation): The provider absorbs the amount unless the patient was notified in advance that the service would not be covered.
  • PR (Patient Responsibility): The patient is responsible, for example when a valid advance notice was signed before a screening service outside the age range.
Official description
Not covered when the patient is under age 35.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What M37 means

Some benefits are tied to age. M37 says the payer compared the patient’s date of birth to the date of service and found the patient was under 35, which is below the minimum age for the service billed. It is often paired with CARC 6, which flags an age conflict between the procedure and the patient.

This remark originated with Medicare but can be used by any payer with an age-35 rule.

Common causes

  • A screening service with an age floor was performed on a younger patient.
  • The patient’s date of birth was entered incorrectly in the practice system or the payer’s records.
  • The service was diagnostic but was coded as a screening service.
  • The wrong patient’s demographics were attached to the claim.

How to fix it

  1. Verify the date of birth against the patient’s ID and the payer’s eligibility response.
  2. If the birth date is wrong, correct it (box 3) and submit a corrected claim with resubmission code 7.
  3. If the service was diagnostic, make sure the codes, diagnosis (box 21), and documentation reflect that, then resubmit or appeal.
  4. If the patient truly did not meet the age requirement, bill the patient only if a valid advance notice was obtained.

How to prevent it

Build age checks into scheduling for services with age limits, and verify demographics at check-in. Pre-submission checks with the Claims Validator can flag age and procedure conflicts. See eligibility and COB denials for demographic verification tips.

Codes that may appear with M37

  • CO-6 (The procedure/revenue code is inconsistent with the patient's age.): The procedure is inconsistent with the patient's age.
  • CO-96 (Non-covered charge(s).): The service is non-covered for a patient of this age.
  • N129 (Not eligible due to the patient's age.): A general age-eligibility remark without a specific age threshold.
  • M82 (Service is not covered when patient is under age 50.): A similar age limit, for services not covered under age 50.
  • M89 (Not covered more than once under age 40.): A frequency limit that applies to patients under age 40.

M37 FAQ

Which services have an age 35 threshold?

An example is Medicare's screening mammography benefit, which allows one baseline exam for women aged 35 through 39, with annual screening from age 40. Other payers may set age 35 limits for other services.

What if the patient's birth date is wrong on file?

Correct the date of birth in box 3 of the claim and with the payer's eligibility records, then resubmit.

Can a diagnostic service avoid the age limit?

Screening and diagnostic services often have different rules. If the service was diagnostic because of symptoms or findings, it should be coded and documented that way.