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N40 Remark Code: Missing Radiology Films or Images

N40 means the payer needed radiology films or images to review the claim and did not receive them. Without the images, it cannot confirm the service was necessary or performed as billed.

Quick facts

Code
N40 (RARC N40)
Status
Active In use since January 1, 2000; last modified July 1, 2008.
Code set
Remittance Advice Remark Codes (RARC)
Group codes
  • CO (Contractual Obligation): The claim is held or denied until the images are supplied. The provider cannot bill the patient while the documentation can still be sent.
  • PI (Payer Initiated Reduction): A payer-initiated adjustment for missing documentation, seen with some government programs.
Official description
Missing radiology film(s)/image(s).
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What N40 means

For some services, a payer’s reviewer wants to look at the images that support the treatment. A dental reviewer may need to see decay or bone loss before approving a crown or periodontal procedure; a medical reviewer may need images for certain procedures. N40 says the payer did not receive the films or digital images it needed.

It typically explains CARC 16, CARC 252, or, when the claim promised attachments that never arrived, CARC 163.

Common causes

  • The claim was sent without an attachment reference, and images were never uploaded.
  • The images were sent separately without the claim number and could not be matched.
  • Images were too old for the payer’s policy, so they were not accepted as current.
  • The facility took the images, and the treating provider did not have copies to send.

How to fix it

  1. Pull the relevant images from your imaging system, and check their date against the payer’s requirement for recent images.
  2. Label each image with patient name, date, and the tooth or anatomic area.
  3. Submit through the payer’s preferred route, such as an electronic attachment linked to the claim or a portal upload.
  4. Resubmit the claim if required, with a corrected claim (resubmission code 7 on professional claims) and the attachment reference.

How to prevent it

Keep a list of procedures for which each payer routinely requests images, and attach them at the time of claim submission. Where the images belong to another facility, request copies before billing. If attachments keep going missing, review how your clearinghouse links attachments to claims.

Codes that may appear with N40

  • CO-16 (Claim/service lacks information or has submission/billing error(s).): Information needed for adjudication is missing; N40 identifies it as images.
  • CO-252 (An attachment/other documentation is required to adjudicate this claim/service.): An attachment is required, and the required attachment is the images.
  • CO-163 (Attachment/other documentation referenced on the claim was not received.): The images were referenced on the claim as coming separately but were not received.
  • N242 (Incomplete/invalid radiology film(s)/image(s).): Images were received but were incomplete or invalid.
  • M31 (Missing radiology report.): The written radiology report, rather than the images, is missing.
  • N785 (Missing current radiology film/images.): Current radiology images specifically are missing.
  • N927 (Missing/Incomplete/Invalid x-ray.): An X-ray is missing, incomplete, or invalid, used mainly on dental claims.

N40 FAQ

Is N40 mostly a dental code?

It shows up frequently on dental claims, where payers review radiographs for crowns, periodontal treatment, and other major work. Medical payers can also use it when images are needed for review.

Can I send a radiology report instead of images?

Usually not when the payer asked for the images themselves. The report is a separate document. Send what was requested, plus the report if it helps.

How should images be sent?

Most payers accept digital images through an attachment service or portal. Label them with the patient name, date taken, and tooth or body area.