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N91 Remark Code: Services Not Included in Appeal Review

N91 means certain services on the claim were not part of the appeal review. The appeal decision applies only to the lines that were reviewed; the lines marked N91 keep their original adjudication until you request review of them separately.

Quick facts

Code
N91 (RARC N91)
Status
Active In use since January 1, 2000.
Code set
Remittance Advice Remark Codes (RARC)
Group codes
  • CO (Contractual Obligation): The original provider-liability adjustment on the unreviewed line still stands. It remains a write-off unless a later review changes it.
  • PR (Patient Responsibility): If the original decision placed the amount on the patient, that assignment is unchanged because the line was not reconsidered.
Official description
Services not included in the appeal review.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What N91 means

N91 shows up on the remittance that follows an appeal or reconsideration. It separates the service lines that the reviewer actually looked at from the ones they did not. For any line carrying N91, nothing changed: the original reason code, amount, and liability still apply.

This matters because staff often assume an appeal decision closes out the whole claim. N91 tells you part of the claim is still in its original, possibly denied, state.

Common causes

  • The appeal request identified only some service lines or dates of service.
  • Supporting documentation addressed only part of the claim.
  • Some lines were outside the scope of the review level requested, or were already being handled in a separate review.
  • The request for those lines was late or did not follow the payer’s appeal procedure.

What to do

  1. Compare the appeal request with the claim. List the lines marked N91 and confirm whether they were named in your request.
  2. Check the appeal deadline for the original decision on those lines. Many payers count from the date of the initial remittance, not the appeal outcome.
  3. File a separate appeal for the unreviewed lines if they are still within the window, naming each service and date and attaching the records that support it.
  4. Write off or bill appropriately if the window has passed, based on the group code on the original adjustment.

How to prevent it

When you appeal, list every disputed line explicitly and tie each one to the documents that support it. An appeal tracker that records which lines were included makes N91 gaps easy to spot. The CARC and RARC analysis guide explains how to read the codes on post-appeal remittances.

Codes that may appear with N91

  • CO-193 (Original payment decision is being maintained.): The original payment decision is being maintained; N91 clarifies that some lines were outside the review entirely.
  • CO-285 (Appeal procedures not followed): Appeal procedures were not followed, one reason a line may have been left out of the review.
  • CO-286 (Appeal time limits not met): Appeal time limits were not met for the lines in question.
  • MA91 (Alert: This determination is the result of the appeal you filed.): Tells you a determination is the result of the appeal you filed, so it covers the lines that were reviewed.
  • N368 (You must appeal the determination of the previously adjudicated claim.): Directs you to appeal the previously adjudicated claim rather than resubmitting.

N91 FAQ

Why would the reviewer skip part of my appeal?

Usually because the request did not list those lines, did not include documentation for them, or they were already under a separate review. The payer's appeal letter or notes may give the specific reason.

Can I still appeal the N91 lines?

Often yes, if the appeal window for the original decision has not closed. File a new request that clearly identifies those services and includes supporting records.

Is N91 a new denial?

No. It does not add a denial; it simply confirms the earlier outcome on those lines was not reconsidered.