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N249 Remark Code: Invalid Assistant Surgeon NPI

N249 means the assistant surgeon's primary identifier, which for HIPAA-covered claims is the National Provider Identifier (NPI), was missing, incomplete, or invalid, so the payer could not identify the provider who assisted.

Quick facts

Code
N249 (RARC N249)
Status
Active In use since December 2, 2004.
Code set
Remittance Advice Remark Codes (RARC)
Group codes
  • CO (Contractual Obligation): The assistant service was denied or rejected for a provider identifier problem. The provider corrects it; the patient is not liable.
Official description
Missing/incomplete/invalid assistant surgeon primary identifier.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What N249 means

Every provider involved in a claim is identified primarily by NPI. N249 says the assistant surgeon’s NPI was not there, was malformed, or did not correspond to a provider the payer can match. It usually explains CARC 16 or one of the NPI-specific codes 206, 207, or 208.

Since assistants usually bill under their own claims with modifier 80, 81, 82, or AS, the NPI in question is typically the rendering NPI in box 24J of the assistant’s claim.

Common causes

  • The surgeon’s NPI was entered in the rendering field on the assistant’s claim.
  • A group (Type 2) NPI was used where an individual (Type 1) NPI is required.
  • A typo failed the NPI check digit.
  • The assistant is not enrolled with the payer, so the NPI doesn’t match.
  • The NPI was deactivated or the assistant’s enrollment ended.

How to fix it

  1. Verify the assistant’s individual NPI in the NPPES registry and confirm it is active.
  2. Confirm the assistant is enrolled with the payer and linked to your group if billing under a group.
  3. Correct box 24J (and box 33a for the group if needed) and submit a corrected claim with resubmission code 7 and the original claim number.
  4. If the claim was rejected at the front end rather than denied, send it as a new, clean claim.

For enrollment and identifier issues, see provider enrollment denials.

How to prevent it

Keep assistants, including non-physician surgical assistants, in the same provider master file as surgeons, with their NPIs and enrollment status by payer. Use claim edits that block an assistant modifier when the rendering NPI matches the primary surgeon.

Codes that may appear with N249

  • CO-16 (Claim/service lacks information or has submission/billing error(s).): The claim contains missing or invalid information; N249 names the assistant's primary ID.
  • CO-206 (National Provider Identifier - missing.): The NPI is missing.
  • CO-207 (National Provider identifier - Invalid format): The NPI has an invalid format.
  • CO-208 (National Provider Identifier - Not matched.): The NPI is not matched to the payer's records.
  • N250 (Missing/incomplete/invalid assistant surgeon secondary identifier.): The assistant surgeon's secondary identifier was missing or invalid.
  • N248 (Missing/incomplete/invalid assistant surgeon name.): The assistant surgeon's name was missing or invalid.
  • N290 (Missing/incomplete/invalid rendering provider primary identifier.): The rendering provider's primary identifier was missing or invalid.

N249 FAQ

What is the primary identifier for an assistant surgeon?

On standard electronic claims it is the individual's NPI. Payers may still use other identifiers internally, but the NPI is the primary one for HIPAA transactions.

Why would a valid-looking NPI be rejected?

It may belong to a group rather than the individual, it may not be enrolled with the payer, or it may fail the check digit because of a typo.

Where does the NPI go on a CMS-1500?

For an assistant billing on their own claim, the individual NPI goes in box 24J as the rendering provider, with the group's NPI in box 33a if billing under a group.