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N27 Remark Code: Missing or Invalid Treatment Number

N27 means the treatment number on the claim was missing, incomplete, or invalid. It usually refers to a payer-issued number, such as a treatment authorization or treatment plan number, that must be reported so the payer can match the claim to approved care.

Code: N27 (RARC N27)
Status: Active In use since January 1, 2000; last modified February 28, 2003.
Code set: Remittance Advice Remark Codes (RARC)
Group codes: CO (Contractual Obligation): The claim is denied as a billing error the provider can correct. It is not billable to the patient.
PI (Payer Initiated Reduction): Some government payers report it as a payer-initiated adjustment. The fix is the same: report the correct number.
Official description: Missing/incomplete/invalid treatment number.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified: September 24, 2026 against the official X12 list.

What N27 means

Some payers assign a number to approved care and require that number on every related claim. N27 tells you the payer could not use the treatment number you reported, or found none at all. The wording is general, so the specific identifier depends on the payer: it is often a treatment authorization number, but it can also be a treatment plan or case number.

N27 usually accompanies CARC 16. If the payer interprets the problem as no valid approval on file, you may see an authorization code such as CARC 197 or CARC 284 instead.

Common causes

The number was never entered on the claim.
Digits were transposed or a prefix or suffix was dropped.
The number belongs to a different patient, provider, or service.
A new number was issued after a renewal, but the old one was billed.
The number was placed in the wrong field, such as box 19 instead of box 23.

How to fix it

Pull the approval letter or portal record for the treatment and confirm the exact number, date range, provider, and approved services.
Correct the claim. Enter the number in box 23 on a CMS-1500 or the treatment authorization code field on a UB-04, formatted exactly as issued.
Send a corrected claim with resubmission code 7 and the original claim number.
If no valid approval exists, contact the payer about retroactive approval options before resubmitting.

How to prevent it

Store treatment and authorization numbers in the patient’s account linked to the services they cover, with expiration dates and remaining units. Build a pre-bill edit that blocks claims for covered services when no current number is attached. For more, see authorization and referral denial prevention.

Codes that may appear with N27

CO-16 (Claim/service lacks information or has submission/billing error(s).): The claim lacks required information; N27 identifies the treatment number.
CO-197 (Precertification/authorization/notification/pre-treatment absent.): When the payer cannot find an approved authorization matching the treatment number, it may report authorization as absent.
CO-284 (Precertification/authorization/notification/pre-treatment number may be valid but does not apply to the billed services.): The authorization number may be valid but does not apply to the billed services.

N54 (Claim information is inconsistent with pre-certified/authorized services.): The claim information does not match the services that were authorized.
N77 (Missing/incomplete/invalid designated provider number.): A different payer-assigned identifier, the designated provider number, is missing or invalid.
CO-15Deactivated (The authorization number is missing, invalid, or does not apply to the billed services or provider.): Older reason code for an authorization number that was missing or invalid, later deactivated.

N27 FAQ

What exactly is a treatment number?

It depends on the payer. Some Medicaid programs issue treatment authorization numbers, and other payers assign numbers to approved treatment plans. Ask the payer which identifier it expected if the remittance does not make it clear.

Where does the number go on a claim?

On a CMS-1500, authorization-type numbers usually go in box 23. On a UB-04, the treatment authorization code field is used. Electronic claims carry it in the prior authorization reference.

What if the authorization expired?

An expired or used-up approval is not a data-entry problem. You may need to request a new or retroactive authorization, if the payer allows it.

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