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N227 Remark Code: Incomplete or Invalid CMN

N227 means the payer received a Certificate of Medical Necessity (CMN) for the item or service, but the form was incomplete or invalid, for example missing answers, signatures, or dates, so it could not support the claim.

Quick facts

Code
N227 (RARC N227)
Status
Active In use since August 1, 2004.
Code set
Remittance Advice Remark Codes (RARC)
Group codes
  • CO (Contractual Obligation): The line was denied because the CMN did not meet requirements. The supplier fixes it; the patient is not liable for this documentation error.
Official description
Incomplete/invalid Certificate of Medical Necessity.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What N227 means

A Certificate of Medical Necessity is a structured form, completed partly by the supplier and partly by the ordering physician, that documents why a patient needs a particular item. When a payer requires one, it checks that each section is filled in correctly. N227 says the CMN on file was there but failed that check. It is common on durable medical equipment claims and typically accompanies CARC 16 or CARC 252.

Common causes

  • One or more medical necessity questions were left blank.
  • The physician’s signature or signature date is missing, or the date is after the item was delivered.
  • The CMN references a different item, HCPCS code, or quantity than the claim.
  • The length of need was blank or conflicts with the order.
  • The supplier completed sections that must be completed by the physician or clinical staff.

How to fix it

  1. Pull the CMN on file and compare it line by line with the payer’s form instructions and the claim.
  2. Identify each deficiency and contact the ordering physician’s office for a revised or new CMN.
  3. Make sure revisions are signed and dated when made, not backdated.
  4. Submit the corrected CMN in the payer’s required format and send a corrected claim with the original claim number if needed.
  5. If the payer no longer requires a CMN for this item, ask why it was applied and request reprocessing.

How to prevent it

Review every CMN for completeness before delivering the item, and use a checklist based on the payer’s instructions. The Claims Validator can help catch claim-level mismatches, such as codes and quantities, before submission.

Codes that may appear with N227

  • CO-16 (Claim/service lacks information or has submission/billing error(s).): The claim has missing or invalid information; the CMN is the problem.
  • CO-252 (An attachment/other documentation is required to adjudicate this claim/service.): Documentation, the CMN, was required and not usable.
  • CO-50 (These are non-covered services because this is not deemed a 'medical necessity' by the payer.): Without a valid CMN, the payer could not establish medical necessity.
  • M60 (Missing Certificate of Medical Necessity.): The Certificate of Medical Necessity was missing entirely.
  • N234 (Incomplete/invalid oxygen certification/re-certification.): Incomplete or invalid oxygen certification or re-certification.
  • M125 (Missing/incomplete/invalid information on the period of time for which the service/supply/equipment will be needed.): Missing or invalid information about the length of need.

N227 FAQ

Are CMNs still used?

Their use has declined. Medicare has moved away from requiring CMNs for many items on recent dates of service, but other payers and some item types may still require a CMN or similar certification. Check the payer's current rules.

What are the most common CMN mistakes?

Unanswered questions, a physician signature missing or dated after delivery, supplier-completed sections that exceed what the supplier may fill in, and length-of-need entries that do not match the order.

Can the physician correct a CMN after the fact?

Corrections usually require a new or revised form signed and dated by the physician when made. Follow the payer's rules on revisions.