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CO-206 Denial Code: NPI Missing

CO-206 means a National Provider Identifier (NPI) is missing from the claim. It could be the billing, rendering, referring, ordering, supervising, or service facility NPI. Add the missing NPI and resubmit; it's usually treated as a correctable billing error.

Code: CO-206 (CARC 206)
Status: Active In use since July 9, 2007; last modified September 30, 2007.
Code set: Claim Adjustment Reason Codes (CARC)
Group codes: CO (Contractual Obligation): The provider is responsible for the missing data. The amount isn't billable to the patient.
Official description: National Provider Identifier - missing.
X12 Claim Adjustment Reason Codes, retrieved September 25, 2026
Last verified: September 24, 2026 against the official X12 list.

What CO-206 means

CARC 206 reads “National Provider Identifier - missing.” HIPAA-covered electronic claims must identify providers by NPI, a 10-digit number assigned by CMS. When a payer needs an NPI for a role on the claim and doesn’t find one, it denies with CO-206.

The CMS-1500 NPI fields are:

Box 33a: billing provider NPI.
Box 24J: rendering provider NPI (shaded area for other IDs, unshaded for NPI).
Box 17b: referring, ordering, or supervising provider NPI.
Box 32a: service facility NPI.

Example: a claim for a referred specialist visit has the referring provider’s name in box 17 but nothing in 17b. The payer requires the referring NPI for this service and denies the claim CO-206 with remark N286.

Common causes

Referring or ordering NPI left blank when the payer requires it.
Rendering NPI missing because a new provider’s profile wasn’t set up in the billing system.
Service facility NPI missing for services outside the billing provider’s office.
Clearinghouse mapping issues that drop NPI fields.
Atypical provider settings used incorrectly for providers who actually have NPIs.

How to fix it

Identify the missing NPI from the remark codes or by checking each NPI field.
Look up the NPI in your records or the NPPES registry.
Submit a corrected claim (resubmission code 7 in box 22) or a new claim if the payer treated the original as unprocessable.
Update provider profiles in your billing system so the NPI populates automatically going forward.

How to prevent it

Set up complete provider profiles before a new clinician’s first claim.
Capture referring and ordering NPIs at scheduling or intake.
Test clearinghouse mapping after system changes.
Scrub claims for blank NPI fields before submission. The Claims Validator flags missing identifiers before the claim leaves. See NPI and enrollment denials and claim rejection vs. denial.

Remark codes that may appear with CO-206

N290 (Missing/incomplete/invalid rendering provider primary identifier.): The rendering provider NPI is missing or invalid.
N286 (Missing/incomplete/invalid referring provider primary identifier.): The referring provider NPI is missing or invalid.
N265 (Missing/incomplete/invalid ordering provider primary identifier.): The ordering provider NPI is missing or invalid.
MA130 (Your claim contains incomplete and/or invalid information, and no appeal rights are afforded because the claim is unprocessable.): The claim is unprocessable. Submit a new claim rather than an appeal.

CO-207 (National Provider identifier - Invalid format): An NPI was present but had an invalid format.
CO-16 (Claim/service lacks information or has submission/billing error(s).): A general missing or invalid information denial, often used with NPI remark codes.
CO-185 (The rendering provider is not eligible to perform the service billed.): The rendering provider is present but not eligible.
CO-183 (The referring provider is not eligible to refer the service billed.): The referring provider is present but not eligible.

CO-206 FAQ

Which NPI is missing?

The remark codes usually tell you: N290 for rendering, N286 for referring, N265 for ordering, and so on. If there's no remark, check every NPI field on the claim.

Is CO-206 a rejection or a denial?

Clearinghouses often reject claims missing a billing NPI before they reach the payer. When the payer adjudicates the claim and denies it, you'll see CO-206 on the ERA. Either way, correct and resubmit.

Should I appeal CO-206?

No. Missing data is fixed by submitting a corrected or new claim with the NPI, following the payer's instructions.

Do atypical providers need an NPI?

Providers who don't perform health care services, such as some transportation or non-medical service vendors, may not be eligible for an NPI and use payer-assigned IDs instead. If a provider is eligible for an NPI, payers generally require it.

Does the individual or group NPI go in box 24J?

Box 24J takes the individual rendering provider's NPI. The group or organization NPI goes in box 33a as the billing provider.

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