Look up another code

N366 Remark Code: Requested Info Not Provided

N366 means the claim was denied because information the payer requested was not provided. The payer will reopen the claim if the previously requested information is submitted within one year after the date of the denial notice.

Code: N366 (RARC N366)
Status: Active In use since April 1, 2006.
Code set: Remittance Advice Remark Codes (RARC)
Group codes: CO (Contractual Obligation): When the provider was asked for the information, the denial is a provider responsibility until the information is sent.
PR (Patient Responsibility): When the patient or member was asked for the information, some payers assign the amount to the patient until it is supplied.
Official description: Requested information not provided. The claim will be reopened if the information previously requested is submitted within one year after the date of this denial notice.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified: September 24, 2026 against the official X12 list.

What N366 means

At some point before this denial, the payer asked for something: medical records, an accident questionnaire, other insurance details, or an itemized bill. It didn’t arrive in time, so the payer closed the claim. N366 tells you the door is still open. Send the requested information within one year of the denial notice and the payer will reopen the claim.

It usually pairs with CARC 226 when the provider was asked, CARC 227 when the patient was asked, or CARC 228 for either.

Common causes

A records request letter went to an old address or a department that didn’t route it to billing.
The patient ignored a questionnaire about accidents or other coverage.
The information was sent but without the claim number or request reference, so it wasn’t matched.
The response was partial, and the payer treated it as not provided.

What to do

Identify the request. Use the payer portal or call provider services to learn what was requested and from whom.
Collect it. If the patient must respond, contact them directly and explain that the claim depends on it.
Send it with identifiers. Include the claim number, the request letter or reference, and the patient’s member ID.
Note the deadline of one year from the denial notice date in your follow-up system.
Confirm reopening. Check the claim status after a few weeks to make sure the information was matched.

How to prevent it

Keep the payer’s correspondence address current and route every request letter to a single queue with due dates. For patient questionnaires, remind the patient at the next visit, and check the portal for pending requests on unpaid claims.

Codes that may appear with N366

CO-226 (Information requested from the Billing/Rendering Provider was not provided or not provided timely or was insufficient/incomplete.): Information requested from the billing or rendering provider was not provided or was insufficient.
CO-227 (Information requested from the patient/insured/responsible party was not provided or was insufficient/incomplete.): Information requested from the patient or insured was not provided or was insufficient.
CO-228 (Denied for failure of this provider, another provider or the subscriber to supply requested information to a previous payer for their adjudication): Denied for failure of the provider, another provider, or the subscriber to supply requested information.

N179 (Additional information has been requested from the member.): Says additional information was requested from the member and the charges will be reconsidered when it arrives.
N888 (Alert: An electronic request for additional information has been sent for this claim.): An alert that an electronic request for additional information was sent for the claim.
N181 (Additional information is required from another provider involved in this service.): Says additional information is required from another provider involved in the service.

N366 FAQ

Do I need to file an appeal?

Usually not. N366 says the payer will reopen the claim if you send the requested information within one year of the denial notice.

What if I never received the request?

Call the payer to find out what was asked for, when, and where it was sent. Then send the information and verify the payer's mailing address for your practice.

What happens after one year?

The remark only promises reopening within that year. After that, check whether the payer's appeal or reopening rules offer any other route.

Important: read before using this information

This page is general educational information about a standard industry code set. It is not medical billing, coding, legal, reimbursement, or compliance advice, and it does not create a professional or advisory relationship with ClaimsRevenue.

Code definitions, payer usage, contracts, and laws change, and payers may apply the same code differently. The information is provided “as is,” without warranties of any kind, express or implied, including accuracy, completeness, or currency. You are solely responsible for verifying it against the current official X12 code lists, CMS guidance, your payer contracts, and payer policies before relying on it, and for every billing, coding, collection, and appeal decision you make.

Using this information does not guarantee that any claim will be paid or that any appeal will succeed. To the fullest extent permitted by law, ClaimsRevenue and MOODRX LLC are not liable for any loss or damage arising from its use. Official code descriptions are published by X12 and are quoted for reference only. See our full Claims Validation Disclaimer.