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M1 Remark Code: X-Ray Too Old for Treatment Course

M1 means the payer did not accept the x-ray used to support the service because it was not taken within the past 12 months or near enough to the start of the course of treatment. It most often appears on chiropractic manipulation claims.

Code: M1 (RARC M1)
Status: Active In use since January 1, 1997.
Code set: Remittance Advice Remark Codes (RARC)
Group codes: CO (Contractual Obligation): The provider absorbs the denied amount because the documentation requirement tied to the x-ray date was not met.
PR (Patient Responsibility): The patient may be responsible, typically only where a valid advance beneficiary notice or plan disclosure was obtained before the service.
Official description: X-ray not taken within the past 12 months or near enough to the start of treatment.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified: September 24, 2026 against the official X12 list.

What M1 means

M1 tells you the payer looked at the x-ray date reported on the claim and decided it was too old, or too far from the start of treatment, to support the service. The remark is rooted in chiropractic coverage rules, where an x-ray is one of the accepted ways to show a spinal subluxation that justifies manual manipulation.

The remark does not stand alone. It explains a reason code, usually a medical necessity denial (CARC 50) or a missing-information denial (CARC 16).

Common causes

The x-ray was taken more than 12 months before the course of treatment began. Medicare generally accepts an x-ray taken no more than 12 months before or 3 months after the start of the course of treatment, with limited exceptions for chronic conditions.
The x-ray was taken more than 3 months after the course of treatment began.
The date was keyed incorrectly, for example the year was wrong.
The practice reused an old x-ray date for a new episode of care.
The claim relied on an x-ray when a documented physical exam would have been the stronger support.

How to fix it

Check the x-ray date on the claim against the imaging report. A typo is the fastest fix.
Confirm when the current course of treatment started and compare that to the x-ray date.
If the date was wrong, send a corrected claim with frequency/resubmission code 7 and the accurate date in box 19 (or the electronic equivalent).
If the subluxation was documented by physical exam, make sure the record reflects it and follow the payer’s reopening or appeal process.
If no qualifying evidence exists, the denial generally stands. Do not bill the patient unless a valid advance notice was signed.

How to prevent it

Set a check in your intake process that flags any chiropractic claim where the x-ray date is older than a year or the episode is new. Tie the x-ray or exam date to each episode of care rather than to the patient. Chiropractic claims also need the active-treatment modifier AT where it applies; see the CO-16 guide for how missing claim data drives denials.

Codes that may appear with M1

CO-50 (These are non-covered services because this is not deemed a 'medical necessity' by the payer.): The service was judged not medically necessary because the supporting x-ray evidence did not qualify.
CO-16 (Claim/service lacks information or has submission/billing error(s).): The claim lacked a usable x-ray date or other required chiropractic information.
CO-96 (Non-covered charge(s).): Some payers report the service as non-covered when the qualifying documentation is missing.

CO-50 (These are non-covered services because this is not deemed a 'medical necessity' by the payer.): The underlying medical necessity denial that M1 explains.
MA121 (Missing/incomplete/invalid x-ray date.): The x-ray date is missing or invalid on the claim, rather than present but outside the window.
M111 (We do not pay for chiropractic manipulative treatment when the patient refuses to have an x-ray taken.): Manipulation is not paid because the patient refused the x-ray altogether.
M127 (Missing patient medical record for this service.): Points to missing patient medical records instead of an x-ray timing problem.

M1 FAQ

Does Medicare still require an x-ray for chiropractic claims?

Medicare allows subluxation to be demonstrated either by x-ray or by a documented physical examination. M1 applies when the claim relies on an x-ray that falls outside the accepted time window.

Where does the x-ray date go on a paper claim?

For Medicare chiropractic claims, the x-ray date is reported in box 19 of the CMS-1500 when an x-ray was used to demonstrate the subluxation. Electronic claims carry it in the corresponding claim segment.

Can I just resubmit with a new x-ray?

If a new x-ray was taken within the window and supports the treatment, you can submit a corrected claim with the updated date. If no qualifying x-ray or exam exists, the denial usually stands.

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