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N255 Remark Code: Billing Provider Taxonomy Invalid

N255 means the taxonomy code identifying the billing provider's specialty or provider type was missing, incomplete, or invalid. Payers use it to route the claim to the right fee schedule and enrollment record, so a bad value stops processing.

Quick facts

Code
N255 (RARC N255)
Status
Active In use since December 2, 2004.
Code set
Remittance Advice Remark Codes (RARC)
Group codes
  • CO (Contractual Obligation): Contractual/provider-correctable. Fix the taxonomy and resubmit; do not bill the patient.
Official description
Missing/incomplete/invalid billing provider taxonomy.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What N255 means

A taxonomy code is a 10-character value that describes what kind of provider an entity is: a multispecialty group, a clinical laboratory, a home health agency, a psychologist, and so on. The billing provider (the group or organization submitting the claim and receiving payment) reports its taxonomy so the payer can match the NPI to the correct enrollment and pricing.

N255 appears when that taxonomy is not there, is not a real code, or does not agree with what the payer has on file for the billing NPI. Payers often couple it with CARC 16.

Common causes

  • A payer that shares one NPI across several enrollments needs the taxonomy to know which one applies, and none was sent.
  • The group’s taxonomy on the claim differs from the one listed in NPPES or on the enrollment application.
  • An individual’s taxonomy (for example, a physician specialty) was sent at the billing level for a group that enrolled as a clinic or multispecialty practice.
  • The value was entered without its qualifier on paper, or with a typo that makes it an unknown code.

How to fix it

  1. Check the taxonomy on the claim against the payer’s enrollment confirmation letter or portal record for your billing NPI.
  2. Compare both with your NPPES entry. If NPPES is out of date, update it, and ask the payer whether its file also needs a change.
  3. Correct the billing provider taxonomy in your practice management system for that payer.
  4. Resubmit a corrected claim (frequency code 7 in box 22 on paper, or the equivalent claim frequency code electronically) with the original claim number.

How to prevent it

Treat taxonomy as enrollment data, not as a billing preference. Record which taxonomy each payer enrolled you under, and update it whenever you add a location or specialty. A pre-submission check with Claims Validator can flag claims whose billing taxonomy is blank or does not match your configured value. For the broader enrollment picture, see NPI, TIN, and network denials.

Codes that may appear with N255

  • CO-16 (Claim/service lacks information or has submission/billing error(s).): Information is missing or invalid; N255 names the billing provider taxonomy as the problem.
  • CO-A1 (Claim/Service denied.): A generic denial where N255 supplies the specific reason.
  • CO-170 (Payment is denied when performed/billed by this type of provider.): May appear when the taxonomy submitted maps to a provider type the payer will not pay for this service.
  • N94 (Claim/Service denied because a more specific taxonomy code is required for adjudication.): Says a more specific taxonomy is required, rather than one that is missing or invalid.
  • N288 (Missing/incomplete/invalid rendering provider taxonomy.): The taxonomy problem for the rendering provider instead of the billing entity.
  • N257 (Missing/incomplete/invalid billing provider/supplier primary identifier.): Addresses the billing provider's NPI instead of its taxonomy.

N255 FAQ

Where does billing provider taxonomy go on a CMS-1500?

It goes in the shaded top portion of box 33b preceded by the ZZ qualifier. On an 837P it is reported as the billing provider's specialty information.

And on a UB-04?

Institutional claims report billing provider taxonomy in form locator 81 with the B3 qualifier.

My group has several specialties. Which taxonomy do I use?

Use the taxonomy tied to the enrollment the payer uses for this group NPI. If the payer enrolled you under multiple taxonomies, it may route claims differently depending on which one you send.