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N940 Remark Code: Pre/Post-Op X-Ray Issue

N940 means the pre-operative and/or post-operative x-ray was missing, incomplete, or invalid. The payer wants radiographic proof of the condition before treatment, the result after, or both, but the remark does not specify the type of image.

Quick facts

Code
N940 (RARC N940)
Status
Active In use since July 1, 2026.
Code set
Remittance Advice Remark Codes (RARC)
Group codes
  • CO (Contractual Obligation): The unpaid amount while the before or after image is outstanding. It is the provider's documentation responsibility.
Official description
Missing/Incomplete/Invalid pre- and/or post-operative x-ray.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What N940 means

N940 is the general before-and-after imaging remark. Where N931 and N932 name specific dental views, N940 only says a pre-operative and/or post-operative x-ray is the problem. That leaves you to work out which image and which timing the payer needs.

The pre-operative image justifies the procedure. The post-operative image shows it was done. A payer may use N940 when either is absent, unreadable, or not clearly tied to the claim.

Common causes

  • Only one of the two images was sent.
  • Images were not labeled as pre or post, or not dated.
  • The images show a different site or tooth than the one billed.
  • The image quality is too poor to interpret.

How to fix it

  1. Check the denial and the payer’s policy to learn whether pre, post, or both are needed.
  2. Pull and label the images with patient, date taken, area, and whether each is pre or post.
  3. Submit them through the payer’s attachment channel with a reprocessing request, or with an appeal if the claim is final.

How to prevent it

For procedures that often require before-and-after imaging, save images to the record with a standard pre-op or post-op label so they are easy to find at billing time.

Codes that may appear with N940

  • CO-252 (An attachment/other documentation is required to adjudicate this claim/service.): An attachment is required; N940 names a before and/or after x-ray.
  • CO-250 (The attachment/other documentation that was received was the incorrect attachment/document.): The wrong image was received, such as a pre-operative film when the post-operative one was needed.
  • CO-251 (The attachment/other documentation that was received was incomplete or deficient.): The image received was incomplete or deficient.
  • N931 (Missing/Incomplete/Invalid pre- and/or post-operative bitewing or periapical x-ray.): Specifies bitewing or periapical before-and-after images.
  • N932 (Missing/Incomplete/Invalid pre- and/or post-operative full mouth x-ray.): Specifies a before-and-after full mouth series.
  • N933 (Missing/Incomplete/Invalid pre- and/or post-operative photo(s).): Before-and-after photographs instead of x-rays.
  • N927 (Missing/Incomplete/Invalid x-ray.): An x-ray is needed, without the before-and-after timing.

N940 FAQ

How do I know which view to send?

Use the payer's policy for the procedure. If it doesn't say, send the images that best show the treated area before and after, and consider calling the payer first.

Does N940 apply only to dental claims?

It is common in dental billing, but its wording is general, so a payer could use it on any claim where before-and-after imaging supports the service.

What if only the pre-op image exists?

Send what you have and explain. The payer may still require a post-operative image to confirm completion, depending on its policy.