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N170 Remark Code: New or Renewed CMN Needed

N170 means a new, revised, or renewed certificate of medical necessity (CMN) is needed. The CMN on file has expired, no longer matches the item or the patient's needs, or was never accepted, so the payer will not pay until an updated one is submitted.

Quick facts

Code
N170 (RARC N170)
Status
Active In use since February 28, 2003.
Code set
Remittance Advice Remark Codes (RARC)
Group codes
  • CO (Contractual Obligation): Payment waits on the supplier's documentation. The supplier obtains the updated certificate; the patient is not billed for the denial.
Official description
A new/revised/renewed certificate of medical necessity is needed.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What N170 means

A certificate of medical necessity documents why a patient needs a particular piece of equipment or supply. It has a start date, a length of need, and details such as the prescribed settings or quantities. N170 tells you the certificate the payer has does not cover this claim: it is expired, outdated, or for something different.

It is most common with durable medical equipment and supplies billed over long periods.

Common causes

  • The length of need on the original certificate ended, and no renewal was obtained.
  • The prescribed amount, flow rate, or item changed, requiring a revised certificate.
  • The patient had a break in need or a new episode, requiring a new certificate.
  • The supplier changed, and the new supplier did not obtain its own certificate where one was required.
  • The payer did not accept a previously sent certificate.

What to do

  1. Review the certificate on file with the payer and your own copy, checking dates, length of need, and the details it certifies.
  2. Determine which type is needed: new, revised, or renewed.
  3. Send the form to the physician with the relevant fields highlighted, and get it signed and dated.
  4. Submit the updated certificate as the payer requires, with the claim or separately, and then resubmit or ask for reprocessing.

How to prevent it

Track certificate expiration and length-of-need dates in your billing system and start renewal requests weeks in advance. Whenever an order changes, check whether the change requires a revised certificate. The missing information guide covers related documentation denials.

Codes that may appear with N170

  • CO-16 (Claim/service lacks information or has submission/billing error(s).): The claim lacks information needed for adjudication, here a current CMN.
  • CO-252 (An attachment/other documentation is required to adjudicate this claim/service.): An attachment or other documentation is required to adjudicate this claim.
  • CO-176 (Prescription is not current.): The prescription is not current.
  • M60 (Missing Certificate of Medical Necessity.): The certificate of medical necessity is missing entirely.
  • N227 (Incomplete/invalid Certificate of Medical Necessity.): The certificate of medical necessity is incomplete or invalid.
  • M42 (The medical necessity form must be personally signed by the attending physician.): The medical necessity form must be personally signed by the attending physician.

N170 FAQ

What is the difference between new, revised, and renewed?

A new CMN is needed when a new item or episode starts; a revised one when information on the current CMN changes, such as the prescribed amount; a renewed one when the certification period ends and the payer requires recertification. Payer rules define each.

Do all payers still use CMNs?

No. Medicare has retired most CMN forms and relies on orders and medical records for many items. Other payers may still require certificates or similar forms, so follow the payer's current policy.

Who completes the CMN?

The treating physician or practitioner completes and signs the medical portions. The supplier may fill in administrative fields but not the medical necessity answers.