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M17 Remark Code: Paid Once, Future Liability Warning

M17 is an alert that the payer paid a service it would not normally cover, because you did not and could not reasonably have known it was non-covered. It warns that you will be liable for the same service under similar conditions in the future.

Quick facts

Code
M17 (RARC M17)
Status
Active In use since January 1, 1997; last modified April 1, 2007.
Code set
Remittance Advice Remark Codes (RARC)
Group codes
  • CO (Contractual Obligation): Any adjustment on the line follows the contract. Going forward, similar services would be the provider's liability unless the patient is properly notified.
Official description
Alert: Payment approved as you did not know, and could not reasonably have been expected to know, that this would not normally have been covered for this patient. In the future, you will be liable for charges for the same service(s) under the same or similar conditions.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What M17 means

Medicare’s limitation of liability rules protect providers and patients who could not reasonably have known that a service would be denied as not reasonable and necessary. M17 says the payer applied that protection in your favor: it paid this time because you were not on notice. The same remark also puts you on notice. Next time, under the same or similar circumstances, you will be considered to have known.

It is a Medicare alert, and it usually accompanies a line that was paid despite a medical necessity or coverage issue.

What to do

  1. Post the payment. No correction or refund is needed.
  2. Record the warning on the patient account and in your coverage notes for the service.
  3. Review the coverage policy for the service so staff know when it is not covered.
  4. Use an advance beneficiary notice before providing the service again in similar conditions, and append the GA modifier when a valid notice is on file.

Keep a log of M17 alerts by service. They tell you where your front-end coverage checks have gaps before those gaps start costing money. See authorization and referral denials for related front-end controls.

Codes that may appear with M17

  • CO-50 (These are non-covered services because this is not deemed a 'medical necessity' by the payer.): The service is one the payer normally treats as not medically necessary.
  • CO-96 (Non-covered charge(s).): The service is normally non-covered for this patient.
  • M27 (Alert: The patient has been relieved of liability of payment of these items and services under the limitation of liability provision of the law.): The opposite outcome: the patient is protected and the provider is liable because it should have known.
  • M38 (Alert: The patient is liable for the charges for this service as they were informed in writing before the service was furnished that we would not…): The patient is liable because they were informed in writing before the service.
  • M39 (Alert: The patient is not liable for payment of this service as the advance notice of non-coverage you provided the patient did not comply with…): The patient is not liable because the advance notice did not meet program requirements.

M17 FAQ

What should I change after receiving M17?

Treat this kind of service as potentially non-covered for this patient. Before furnishing it again, give the patient a valid advance beneficiary notice where the payer requires one.

Do I have to return the payment?

No. M17 accompanies a payment the payer chose to make under the limitation of liability rules. It is a warning for next time.

Does M17 apply to other patients too?

The remark refers to the same or similar services under the same or similar conditions. It is sensible to update your process for all similar cases, not just this patient.