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MA123 Remark Code: Center Not Selected for Study

MA123 means the payer cannot pay for the services because your center was not selected to participate in the study under which they were billed.

Quick facts

Code
MA123 (RARC MA123)
Status
Active In use since January 1, 1997.
Code set
Remittance Advice Remark Codes (RARC)
Group codes
  • CO (Contractual Obligation): Payment is denied because the facility is not an approved study site. Patient billing depends on whether any advance notice was given and on payer rules.
Official description
Your center was not selected to participate in this study, therefore, we cannot pay for these services.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What MA123 means

Some Medicare studies or demonstrations pay only at selected sites. MA123 tells you your center was not among the selected sites for the study these services were billed under, so the payer cannot pay for them. The problem is the facility’s status, not the patient’s eligibility or coding.

Common causes

  • The center billed study services before its selection was confirmed.
  • The center applied but was not selected.
  • Study coding was applied to a routine service that should have been billed normally.
  • The payer’s list of participating sites was not updated.

What to do

  1. Confirm your center’s status with the study sponsor or program.
  2. Request reprocessing with proof if your center was selected.
  3. Rebill as a routine service if it qualifies for coverage outside the study, removing study coding.
  4. Write off services that cannot be paid, following your policy and payer rules on patient liability.

How to prevent it

  • Do not bill study-specific services until site selection is confirmed in writing.
  • Keep a record of all studies your center participates in and their effective dates.
  • Coordinate research and billing teams; see authorization and referral denials for general approval workflows.

Codes that may appear with MA123

  • CO-B7 (This provider was not certified/eligible to be paid for this procedure/service on this date of service.): The provider was not certified or eligible to be paid for this service.
  • CO-96 (Non-covered charge(s).): A non-covered charge because study participation was not approved.
  • MA84 (Patient identified as participating in the National Emphysema Treatment Trial but our records indicate that this patient is either not a…): A study remark about the patient not being an approved participant, rather than the center.
  • MA97 (Missing/incomplete/invalid Medicare Managed Care Demonstration contract number or clinical trial registry number.): A missing demonstration contract or clinical trial number.

MA123 FAQ

Can I appeal MA123?

Only if your center was in fact selected. Gather proof of your approval and use the payer's appeal or reopening process.

Can I bill the patient?

Under the CO group code, generally no. Whether the patient can be billed depends on payer rules and any advance notice given.

Can I rebill the service outside the study?

If the service is covered under normal rules, remove study coding and bill it as a standard claim. Otherwise, it is not payable.