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N350 Remark Code: Missing NOC or Unlisted Code Description

N350 means a not otherwise classified (NOC) code or an unlisted or by-report procedure was billed without a complete, valid description of the service, so the payer could not tell what was performed or supplied.

Quick facts

Code
N350 (RARC N350)
Status
Active In use since August 1, 2005; last modified July 1, 2008.
Code set
Remittance Advice Remark Codes (RARC)
Group codes
  • CO (Contractual Obligation): The line was denied because the payer could not identify the service. The provider adds the description and resubmits; the patient is not billed.
Official description
Missing/incomplete/invalid description of service for a Not Otherwise Classified (NOC) code or for an Unlisted/By Report procedure.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What N350 means

NOC and unlisted codes are placeholders used when no specific code describes the service, drug, or supply. Because the code alone says nothing about what was done, payers require a written description on the claim. N350 tells you the description was missing, cut off, or not meaningful enough to process.

The remark usually explains CARC 16. When the payer needs more than a line of text, CARC 252 may ask for documentation. If the description reveals a specific code was available, the payer may deny with CARC 189 instead.

Common causes

  • The claim was sent without any narrative for the NOC line.
  • The description was truncated because it exceeded the field’s character limit.
  • The text was generic, such as “unlisted procedure” or “drug,” with no specifics.
  • The description landed in the wrong field, like the claim-level note, when the payer reads line-level notes.
  • For drugs billed with a NOC code, the NDC, dose, or unit of measure was missing.

How to fix it

  1. Write a clear description. For a drug, include the drug name, strength, dose given, and route. For a procedure, describe the service briefly and name a comparable code if the payer requests one.
  2. Put it in the right place. Use the line-level description field on the 837P, or box 19 or the shaded area of 24 on paper, as the payer instructs.
  3. Prepare support. Attach the operative note, invoice, or medication record if the payer prices NOC lines manually.
  4. Confirm no specific code exists. Check current HCPCS and code set updates for the date of service.
  5. Resubmit as a corrected claim with frequency code 7 and the original claim number.

How to prevent it

Set a hard stop in charge entry so NOC and unlisted codes cannot be released without a description. Keep a payer-specific template for common NOC items, and review code updates each quarter because new specific codes often replace NOC reporting.

Codes that may appear with N350

  • CO-16 (Claim/service lacks information or has submission/billing error(s).): Information is missing; N350 identifies the description of the NOC or unlisted service.
  • CO-252 (An attachment/other documentation is required to adjudicate this claim/service.): Documentation is required, such as an operative note or invoice supporting the unlisted service.
  • CO-189 ('Not otherwise classified' or 'unlisted' procedure code (CPT/HCPCS) was billed when there is a specific procedure code for this procedure/service): A NOC or unlisted code was billed when a specific code exists, which the payer may conclude after reading the description.
  • M20 (Missing/incomplete/invalid HCPCS.): Used when the HCPCS code itself is missing or invalid.
  • M51 (Missing/incomplete/invalid procedure code(s).): Covers missing or invalid procedure codes in general.
  • N354 (Incomplete/invalid invoice.): Used when an invoice is incomplete or invalid, often requested for NOC supplies and drugs.

N350 FAQ

Where does the description go?

On an electronic 837P, most payers read the description from the line-level note or description field. On the CMS-1500, it is typically placed in the shaded area of box 24 or in box 19, depending on payer instructions.

How detailed should the description be?

Enough for a reviewer to know exactly what was done or supplied. For drugs, include the name, dose, and route. For procedures, a short clinical description and any comparable code the payer asks for.

Will I need to send records?

Often. Many payers price unlisted procedures manually and ask for the operative report or invoice along with the description.