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MA63 Remark Code: Principal Diagnosis Missing or Invalid

MA63 means the payer could not process the claim because the principal diagnosis was missing, incomplete, or not a valid ICD-10-CM code. Add or correct the principal diagnosis and resubmit.

Quick facts

Code
MA63 (RARC MA63)
Status
Active In use since January 1, 1997; last modified February 28, 2003.
Code set
Remittance Advice Remark Codes (RARC)
Group codes
  • CO (Contractual Obligation): The claim or line was not paid because of the diagnosis error. The provider must correct it; the patient is not billed.
Official description
Missing/incomplete/invalid principal diagnosis.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What MA63 means

MA63 tells you the principal diagnosis on the claim could not be used. It was either left blank, submitted with too few characters, or not a valid ICD-10-CM code for the date of service. Payers use MA63 mainly on institutional claims (UB-04 / 837I), where the principal diagnosis is its own field (form locator 67) separate from other diagnoses. It usually explains CARC 16, which signals the claim lacked information needed for adjudication.

Common causes

  • The principal diagnosis field was empty because the chargemaster or abstracting step did not populate it.
  • A code was truncated, for example a category code submitted without its required 5th, 6th, or 7th character.
  • The code was deleted or not yet effective on the date of service after an annual ICD-10-CM update.
  • A code designated for secondary use only (such as some external cause codes) was placed in the principal position.
  • Data was lost when the claim was converted from paper or passed through a clearinghouse.

How to fix it

  1. Read the ERA to confirm MA63 applies to the claim and see which CARC accompanies it.
  2. Review the medical record and confirm the condition chiefly responsible for the encounter.
  3. Validate the code against the ICD-10-CM code set in effect on the date of service, including all required characters.
  4. Correct the claim so the principal diagnosis is in the right field and position.
  5. Resubmit. If the claim was returned as unprocessable, submit it as a new claim. If the payer processed it and you are replacing it, use the payer’s corrected-claim process (for institutional claims, the appropriate type-of-bill frequency code). See CO-16 and missing information denials.

How to prevent it

  • Update diagnosis tables promptly each October when ICD-10-CM changes take effect.
  • Add an edit that blocks institutional claims with a blank or non-billable principal diagnosis.
  • Have coders confirm that secondary-only codes never land in the principal position.

Codes that may appear with MA63

  • CO-16 (Claim/service lacks information or has submission/billing error(s).): The most common pairing: the claim lacks information needed for adjudication, and MA63 names the principal diagnosis as the problem.
  • CO-146 (Diagnosis was invalid for the date(s) of service reported.): The diagnosis was invalid for the date of service, for example a code that was deleted or not yet effective.
  • CO-11 (The diagnosis is inconsistent with the procedure.): The diagnosis was present but inconsistent with the procedure billed.
  • MA65 (Missing/incomplete/invalid admitting diagnosis.): The admitting diagnosis, a separate field reported on inpatient claims.
  • M76 (Missing/incomplete/invalid diagnosis or condition.): A general missing or invalid diagnosis remark, often used on professional claims.
  • M81 (You are required to code to the highest level of specificity.): The diagnosis was not coded to the highest level of specificity.
  • MA66 (Missing/incomplete/invalid principal procedure code.): The inpatient counterpart for the principal procedure code.

MA63 FAQ

What is the principal diagnosis?

On institutional claims it is the condition established after study to be chiefly responsible for the admission or the outpatient encounter. On the UB-04 it is reported in form locator 67.

Is MA63 a denial or a rejection?

It is usually treated as an unprocessable claim, so there are generally no appeal rights. Correct the diagnosis and submit again rather than appealing.

Can a truncated code trigger MA63?

Yes. An ICD-10-CM code that is missing required characters is considered invalid, so the principal diagnosis must be coded to its full length.