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N42 Remark Code: Missing Mental Health Assessment

N42 means the payer needed a mental health assessment to process the claim and did not receive it. The assessment documents the patient's condition and need for treatment, and some payers require it before paying behavioral health services.

Code: N42 (RARC N42)
Status: Active In use since January 1, 2000; last modified November 1, 2014.
Code set: Remittance Advice Remark Codes (RARC)
Group codes: CO (Contractual Obligation): The service is denied until the assessment is provided. The provider cannot bill the patient for it while the documentation can be supplied.
PI (Payer Initiated Reduction): Some government programs report the missing assessment as a payer-initiated adjustment.
Official description: Missing mental health assessment.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified: September 24, 2026 against the official X12 list.

What N42 means

Behavioral health services often depend on a documented assessment that establishes the diagnosis, the severity of symptoms, and why a particular level of care is appropriate. N42 tells you the payer looked for that assessment and did not find it. The treatment may be fully covered once the payer can see the assessment.

N42 is usually tied to CARC 16 or CARC 252. If the payer instead concluded the service was not justified, CARC 50 may appear.

Common causes

A payer or program requires an initial assessment before ongoing treatment, and it was not submitted.
A records request was sent to the practice but not answered.
The assessment existed but was sent without the claim or authorization number.
The assessment was out of date for the payer’s rules, such as a program requiring periodic reassessment.

How to fix it

Find the assessment that covers the dates of service, and confirm it was completed by a qualified clinician and signed.
Check that it is current under the payer’s reassessment rules.
Send it the way the payer requests, such as an electronic attachment or portal upload referencing the claim.
Resubmit if needed. If the claim was closed, send a corrected claim (resubmission code 7) or new claim with the attachment.
Complete a new assessment for future dates if the existing one is outdated.

How to prevent it

Track assessment and reassessment dates for each patient, and set reminders ahead of expiration. For programs that require an assessment to accompany authorization or claims, add a pre-bill check that confirms one is on file for the service dates.

Codes that may appear with N42

CO-16 (Claim/service lacks information or has submission/billing error(s).): Information needed for adjudication is missing, and N42 says it is the assessment.
CO-252 (An attachment/other documentation is required to adjudicate this claim/service.): An attachment is required to adjudicate the service; here it is the assessment.
CO-50 (These are non-covered services because this is not deemed a 'medical necessity' by the payer.): Without the assessment, the payer may treat the service as not shown to be medically necessary.

N731 (Incomplete/Invalid mental health assessment.): An assessment was received but was incomplete or invalid.
N237 (Incomplete/invalid patient medical record for this service.): The patient medical record for the service is incomplete or invalid.
N238 (Incomplete/invalid physician certified plan of care.): The physician-certified plan of care is incomplete or invalid.

N42 FAQ

What should a mental health assessment include?

Payers vary, but they generally look for presenting problems, history, mental status findings, diagnosis, functional impact, and a recommended level of care. Check the payer's behavioral health policy for its required elements.

Does every therapy claim need an assessment attached?

No. Payers typically require it for certain services or programs, such as intensive outpatient, partial hospitalization, residential care, or authorization requests, or when a claim is selected for review.

Can an assessment done by another provider be used?

Sometimes. Some programs accept a recent assessment from a qualified provider. Confirm the payer's rules on who may perform it and how recent it must be.

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