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M90 Remark Code: Limited to Once in 12 Months

M90 means the payer covers this service no more than once in a 12-month period, and it was already paid within that window. The later service is denied unless the dates or coding were wrong.

Quick facts

Code
M90 (RARC M90)
Status
Active In use since January 1, 1997.
Code set
Remittance Advice Remark Codes (RARC)
Group codes
  • CO (Contractual Obligation): The repeat service is written off by the provider unless the patient signed an advance notice.
  • PR (Patient Responsibility): The patient owes the amount, generally because a valid advance notice of non-coverage was obtained.
Official description
Not covered more than once in a 12 month period.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What M90 means

M90 is a straightforward frequency limit. The payer covers the service at most one time in any 12-month period. If it already paid for the same service for this patient within that span, the new claim is denied. This rule is common for annual screenings, wellness services, and some routine exams.

The tricky part is counting. A “12-month” rule is not always the same as “once per calendar year.” Many Medicare frequency rules count months: after a service in March, the next covered one is in March of the next year or later. A calendar-year plan benefit, by contrast, may allow a December visit and a January visit.

Common causes

  • A service scheduled a few weeks too early.
  • The patient had the service elsewhere within the past 12 months.
  • An incorrect date of service on either claim.
  • A diagnostic follow-up coded with a screening or routine code.

How to fix it

  1. Find the prior paid date in your records or by asking the payer.
  2. Count the months using the payer’s method and confirm the rule applies.
  3. Correct any date or coding errors and send a corrected claim with frequency code 7.
  4. If the service was necessary for a new problem, recode as diagnostic with documentation, or appeal.
  5. If the denial stands, bill the patient only when an advance notice or plan rule permits it.

How to prevent it

  • Show the last covered date for frequency-limited services at scheduling.
  • Ask patients about services received elsewhere.
  • Use a Claims Validator to flag services that fall inside a known frequency window.

Codes that may appear with M90

  • PR-119 (Benefit maximum for this time period or occurrence has been reached.): The benefit maximum for the 12-month period has been reached.
  • CO-96 (Non-covered charge(s).): The service is non-covered, with M90 giving the frequency reason.
  • M86 (Service denied because payment already made for same/similar procedure within set time frame.): A general same-or-similar service limit within a set time frame, not fixed at 12 months.
  • M89 (Not covered more than once under age 40.): An age-based once-only rule for patients under 40.
  • N416 (This service is allowed 1 time in a 3-year period.): A limit of one service every three years.
  • N640 (Exceeds number/frequency approved/allowed within time period.): A general frequency limit within a time period.

M90 FAQ

Is 12 months the same as once per calendar year?

No. A 12-month period usually means at least 11 full months must pass after the month of the last service. A calendar-year rule resets on January 1. Check which the payer uses.

Does the limit apply across providers?

Yes. If another provider was paid for the service within the window, your claim can be denied.

What if the patient's condition changed?

If the repeat was diagnostic rather than routine, code it with the supporting diagnoses. Some policies allow exceptions with documentation.