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N921 Remark Code: Appeal Time Limit Expired

N921 means the time limit for filing a reconsideration or appeal has expired. The payer did not review the merits of your request because it arrived after the deadline.

Quick facts

Code
N921 (RARC N921)
Status
Active In use since March 1, 2026.
Code set
Remittance Advice Remark Codes (RARC)
Group codes
  • CO (Contractual Obligation): The original denied amount remains a provider write-off because the appeal was not considered. It is not billable to the patient.
Official description
The time limit for filing a reconsideration or appeal has expired.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What N921 means

Every payer gives providers a window to dispute a claim decision, whether through reconsideration, redetermination, or formal appeal. N921 means your request came in after that window closed, so the payer rejected it on procedure rather than on substance.

Common causes

  • The appeal was mailed close to the deadline and arrived late.
  • Staff counted from the wrong date, such as the date the remittance was posted instead of the date issued.
  • A first-level appeal was missed and the request was filed at a later level.
  • The appeal went to the wrong address and was forwarded after the deadline.

What to do

  1. Check the dates. Compare the determination date, the deadline, and your proof of submission.
  2. If you filed on time, resubmit the appeal with proof, such as a fax confirmation, portal receipt, or delivery tracking.
  3. If you were late for a good reason, ask whether the payer accepts good-cause exceptions and submit your explanation.
  4. Otherwise, write off the claim and note the root cause.

How to prevent it

Calendar each denial’s appeal deadline when the remittance posts, not when someone gets to the work queue. Use trackable submission methods and keep receipts. See timely filing denials for broader deadline management.

Codes that may appear with N921

  • CO-286 (Appeal time limits not met): Appeal time limits not met, the reason code that most directly matches N921.
  • CO-285 (Appeal procedures not followed): Appeal procedures were not followed, a related procedural denial.
  • CO-29 (The time limit for filing has expired.): The original claim, rather than the appeal, was filed too late.
  • N892 (The claim does not meet the criteria for acceptable use of the Delay Reason Code.): A delay reason code used to excuse a late claim was not accepted.
  • N368 (You must appeal the determination of the previously adjudicated claim.): You must appeal the earlier claim's determination instead of submitting a new claim.

N921 FAQ

How is N921 different from a timely filing denial?

Timely filing concerns the original claim. N921 concerns the appeal or reconsideration request filed after a claim decision.

Are there exceptions?

Some payers and programs accept late appeals for good cause, such as a payer error or circumstances beyond your control. Check the payer's appeal rules and document the reason.

When does the appeal clock start?

Usually from the date of the initial determination or remittance, but each payer and contract defines it. Read the appeal language on the remittance or in your contract.