Skip to main content

N259 Remark Code: Billing Provider Secondary ID

N259 means an identifier the payer requires for the billing provider or supplier, in addition to the NPI, was missing, incomplete, or invalid. This is often the tax ID (EIN or SSN) or a payer-assigned provider number.

Quick facts

Code
N259 (RARC N259)
Status
Active In use since December 2, 2004.
Code set
Remittance Advice Remark Codes (RARC)
Group codes
  • CO (Contractual Obligation): Correctable by the provider. Fix the secondary identifier and resubmit; nothing is owed by the patient.
Official description
Missing/incomplete/invalid billing provider/supplier secondary identifier.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What N259 means

The NPI is the billing provider’s primary identifier, but it rarely travels alone. Payers also expect at least a tax identification number, and some want an additional number they assigned at enrollment. N259 tells you one of those supporting identifiers was not present or not acceptable.

Most often the payer returns N259 with CARC 16. The claim was not evaluated for coverage; it is waiting on a correct identifier.

Common causes

  • The tax ID on the claim is not the one tied to the billing NPI in the payer’s enrollment file, often after an ownership change.
  • A Social Security number was sent for a group that enrolled with an EIN, or the reverse.
  • A Medicaid or commercial plan requires its own provider number in addition to the NPI, and it was not configured for that payer.
  • The qualifier describing the identifier type was wrong or missing, so the payer could not interpret the number.
  • An atypical provider’s payer-assigned ID expired or was entered with a typo.

Working the denial

  1. Identify which secondary identifier the payer expects. The provider manual or companion guide usually spells this out.
  2. For tax ID issues, compare the claim against your IRS assignment letter and the payer’s enrollment record. A single mismatched digit is enough to fail.
  3. For payer-assigned numbers, confirm the current value in the payer portal or with provider services.
  4. Correct the billing provider setup for that payer, including the qualifier.
  5. Resubmit with frequency code 7 and the original claim number, unless the payer says a new claim is needed.

Our guide to NPI, TIN, and enrollment denials covers tax ID mismatches in more depth.

How to prevent it

Keep NPI, tax ID, and any payer-specific numbers together in one provider record, with effective dates. When your tax ID changes after a sale or restructuring, re-enroll or update every payer before switching the ID on outgoing claims.

Codes that may appear with N259

  • CO-16 (Claim/service lacks information or has submission/billing error(s).): The claim lacks required information; N259 points to the billing provider's secondary identifier.
  • N257 (Missing/incomplete/invalid billing provider/supplier primary identifier.): Concerns the billing provider's primary identifier (NPI).
  • N209 (Missing/incomplete/invalid taxpayer identification number (TIN).): Specifically flags a missing or invalid taxpayer identification number.
  • MA113 (Incomplete/invalid taxpayer identification number (TIN) submitted by you per the Internal Revenue Service.): Tells you the TIN submitted does not agree with IRS records.
  • N516 (Records indicate a mismatch between the submitted NPI and EIN.): Flags an NPI and EIN that do not match each other.

N259 FAQ

What is the billing provider's secondary identifier?

On HIPAA electronic claims the billing provider must report its tax ID (EIN, or SSN for some individuals) alongside the NPI. Some payers also require a proprietary provider number or state Medicaid ID.

Where does it go on paper?

The federal tax ID goes in box 25 of the CMS-1500. Other secondary IDs for the billing provider go in box 33b with a qualifier.

Could an atypical provider see N259?

Yes. Providers without an NPI, such as some transportation or non-medical service vendors, rely on payer-assigned IDs, and a missing or wrong one can trigger this remark.