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N409 Remark Code: Accident Care Outside Time Frame

N409 means the service is related to an accidental injury, and the plan covers that kind of care only if it is delivered within a specific time frame after the accident. The service on the claim fell outside that window, or the dates on the claim made it look that way.

Quick facts

Code
N409 (RARC N409)
Status
Active In use since August 1, 2007.
Code set
Remittance Advice Remark Codes (RARC)
Group codes
  • PR (Patient Responsibility): The plan considers the service outside its accident benefit, so the patient may be responsible, subject to your contract and any notice requirements.
  • CO (Contractual Obligation): Some payers report the denial as a provider write-off, for example under network terms. Review the contract before billing the patient.
Official description
This service is related to an accidental injury and is not covered unless provided within a specific time frame from the date of the accident.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What N409 means

Some benefits apply only because an accident happened, and those benefits often carry a deadline. A plan might, for example, cover dental repair after an accidental injury only when care happens within a stated period from the accident. N409 tells you the payer linked the service to an accidental injury and found that it was delivered outside that allowed window.

N409 most often explains CARC 96 or CARC 204. The denial is about timing relative to the accident, not medical necessity.

Where the accident date comes from

The payer calculates the window from the injury date on the claim. On a CMS-1500, the date of current illness or injury is reported in box 14, and box 10 indicates whether the condition is related to employment or an accident. On institutional claims, accident information is carried in occurrence codes and dates. If those fields are wrong or missing, the payer’s calculation will be wrong too.

Common causes

  • Treatment genuinely started after the plan’s accident window closed.
  • The claim reported the date of first visit or the date of the current service instead of the accident date.
  • A later, unrelated condition was coded with an injury diagnosis, so the payer treated it as accident care.
  • Staged treatment continued past the window even though care began on time.

How to fix it

  1. Pull the accident date from the medical record and compare it with what was billed.
  2. If the date was wrong, correct it and send a corrected claim with resubmission code 7 and the original claim number.
  3. If the care was unrelated to the accident, review the diagnosis coding and remove the accident indicators so the claim can process under regular benefits.
  4. If care was delayed for a clinical reason, appeal with the provider’s explanation and records showing why treatment could not start sooner.
  5. If the denial stands, follow your contract and any notice rules before billing the patient.

How to prevent it

Capture the accident date at the first visit and carry it forward on every related claim. For accident benefits with deadlines, check the plan terms early and schedule care with that deadline in mind.

Codes that may appear with N409

  • CO-96 (Non-covered charge(s).): Non-covered charge; N409 explains that the non-coverage comes from the accident benefit's time limit.
  • PR-204 (This service/equipment/drug is not covered under the patient's current benefit plan): The service is not covered under the current benefit plan, with N409 specifying the timing condition that was not met.
  • CO-16 (Claim/service lacks information or has submission/billing error(s).): Can appear when the accident date is missing or unclear, preventing the payer from applying the time limit correctly.
  • N299 (Missing/incomplete/invalid occurrence date(s).): Points to a missing or invalid occurrence date, which often carries the accident date.
  • CO-20 (This injury/illness is covered by the liability carrier.): Used when the injury is the responsibility of a liability carrier instead of the health plan.
  • CO-21 (This injury/illness is the liability of the no-fault carrier.): Used when a no-fault carrier is responsible for the accident-related care.

N409 FAQ

How long is the accident time frame?

It depends on the plan. Some accident benefits, such as those for accidental dental injuries, require treatment to start or finish within a set period after the injury. Check the patient's benefit documents for the exact rule.

What if the accident date on the claim is wrong?

Correct it and submit a corrected claim. An incorrect injury date can make timely treatment look late and trigger N409 on its own.

Can a treatment delay be justified on appeal?

Sometimes. If treatment was delayed for medical reasons, such as waiting for swelling or healing, a letter from the treating provider with supporting records may persuade the plan to make an exception. Approval is not assured.