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MA21 Remark Code: Name and Sex Mismatch With SSA

MA21 means the payer compared the claim with Social Security Administration (SSA) records and found that the patient's name and sex do not match. The claim cannot be processed until the demographic details agree with the beneficiary's record.

Quick facts

Code
MA21 (RARC MA21)
Status
Active In use since January 1, 1997.
Code set
Remittance Advice Remark Codes (RARC)
Group codes
  • CO (Contractual Obligation): The provider must correct the demographic data. The patient should not be billed for a claim returned for mismatched information.
Official description
SSA records indicate mismatch with name and sex.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What MA21 means

MA21 is a demographic match failure. The payer, typically Medicare, checks the name and sex on the claim against the beneficiary’s record, which is based on Social Security data. When both fail to line up, the payer cannot confirm the claim belongs to that beneficiary.

Sex is included in the match, so a claim can fail even with the correct name spelling if the sex field disagrees with the record.

Common causes

  • A typo, nickname, or missing suffix in the patient name in box 2.
  • The sex field in box 3 was entered incorrectly or defaulted in registration.
  • The patient changed their name, but the change is not yet reflected in the beneficiary record.
  • The claim was billed under a family member’s identifier.

How to fix it

  1. Run an eligibility check. Compare the name and sex returned by the payer with what is on the claim.
  2. Correct boxes 2 and 3 to match the eligibility response and the patient’s card.
  3. Resubmit. Send a corrected claim or, for a claim that was processed and denied, a replacement with resubmission code 7 in box 22.
  4. Refer the patient to Social Security if the record itself is wrong, and hold the claim until it is updated.

How to prevent it

Copy the name exactly as shown on the insurance card and confirm demographics with a real-time eligibility response. A Claims Validator that compares demographics before submission catches these mismatches early. More in claim rejection vs. denial.

Codes that may appear with MA21

  • CO-16 (Claim/service lacks information or has submission/billing error(s).): The claim lacks valid information for adjudication, with MA21 naming the demographic mismatch.
  • CO-140 (Patient/Insured health identification number and name do not match.): The patient's identification number and name do not match.
  • CO-31 (Patient cannot be identified as our insured.): The patient cannot be identified as the payer's insured.
  • MA36 (Missing/incomplete/invalid patient name.): The patient name is missing, incomplete, or invalid.
  • MA39 (Missing/incomplete/invalid gender.): The patient's gender is missing, incomplete, or invalid.
  • MA27 (Missing/incomplete/invalid entitlement number or name shown on the claim.): The entitlement number or name on the claim is missing or invalid.

MA21 FAQ

Why would Medicare check SSA records?

Medicare beneficiary records are tied to Social Security data. When the claim's name and sex do not line up with that data, the payer cannot be sure it is paying for the right person.

What if the patient legally changed their name?

Bill using the name on the patient's Medicare card or eligibility response. The patient should update their record with Social Security so the systems agree.

Is MA21 a rejection or a denial?

It is usually handled as a front-end problem that stops the claim from being paid. Once corrected, the claim can be processed normally.