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N755 Remark Code: Missing or Invalid ICD Indicator

N755 means the ICD indicator on the claim was missing, incomplete, or invalid. The indicator tells the payer which diagnosis code set is used; on the CMS-1500 it appears in box 21, with 0 for ICD-10-CM and 9 for ICD-9-CM.

Quick facts

Code
N755 (RARC N755)
Status
Active In use since July 1, 2015; last modified March 1, 2016.
Code set
Remittance Advice Remark Codes (RARC)
Group codes
  • CO (Contractual Obligation): The claim is denied as a billing error the provider must correct. Not patient responsibility.
Official description
Missing/incomplete/invalid ICD Indicator.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What N755 means

Diagnosis codes only make sense when the payer knows which code set they come from. The ICD indicator carries that information. On the CMS-1500 it is a single digit in box 21, labelled “ICD Ind.”: 0 means ICD-10-CM and 9 means ICD-9-CM. Electronic claims convey the code set through qualifiers on each diagnosis.

N755 means that indicator was blank, unreadable, or did not fit the diagnosis codes. It usually pairs with CARC 16. Because ICD-10-CM has applied to dates of service for years, nearly every claim today should use 0.

Common causes

  • The indicator field in box 21 was left empty on a paper claim.
  • Software printed an outdated default value of 9.
  • Form alignment pushed the digit outside the field, so it was not scanned.
  • The indicator did not match the format of the codes listed.

How to fix it

  1. Check box 21 on the claim image or print file.
  2. Set the indicator to 0 for ICD-10-CM codes.
  3. Confirm each diagnosis code is valid for the date of service and correctly pointed to in box 24E.
  4. Submit a corrected claim with resubmission code 7, or a new claim if the payer rejected the original as unprocessable.

How to prevent it

Make 0 the fixed default in your paper claim template and test print alignment after software updates. Front-end claim checks can catch an empty or mismatched indicator before a paper or electronic claim goes out.

Codes that may appear with N755

  • CO-16 (Claim/service lacks information or has submission/billing error(s).): The claim lacks information or has a billing error; N755 points to the ICD indicator.
  • CO-146 (Diagnosis was invalid for the date(s) of service reported.): The diagnosis was invalid for the dates of service, which can result from a wrong code set indicator.
  • M76 (Missing/incomplete/invalid diagnosis or condition.): The diagnosis itself is missing or invalid, rather than the indicator.
  • M64 (Missing/incomplete/invalid other diagnosis.): An additional diagnosis is missing or invalid.
  • N742Deactivated (Alert: This claim was processed based on one or more ICD-9 codes.): A deactivated alert from the ICD-10 transition about claims processed with ICD-9 codes.

N755 FAQ

What value should the ICD indicator have?

For current dates of service, 0, which means ICD-10-CM. The value 9 means ICD-9-CM, which applies only to very old dates of service.

Where is the ICD indicator on the CMS-1500?

In box 21, in the small field labelled 'ICD Ind.' in the upper right area of the box. The NUCC instructions say to enter it as a single digit between the vertical, dotted lines.

Can a wrong indicator cause other denials?

Yes. If the indicator says ICD-9 but the codes are ICD-10, the payer may read the diagnoses as invalid, producing diagnosis-related denials.