CO-9: Diagnosis Inconsistent with Patient Age

What Does CO-9 Mean?

With CO (Contractual Obligation), the CARC 9 adjustment is the provider's responsibility. The payer denied or reduced payment because of patient's DOB is wrong in the system, causing age to be calculated incorrectly for diagnosis validation. The patient is not liable for this amount. If the denial is in error, the provider can correct and resubmit the claim or file an appeal with supporting documentation.

CARC 9 appears on a remittance when the payer identifies an issue related to diagnosis inconsistent with patient age. This is a technical billing or coding problem that must be corrected before the claim can be processed for payment. The denial indicates the claim data did not meet the payer's adjudication requirements.

Common scenarios that trigger this adjustment include: patient's DOB is wrong in the system, causing age to be calculated incorrectly for diagnosis validation; Diagnosis code has age restrictions that do not match the patient's actual age (e.g., pediatric condition coded for adult); Coder selected an ICD-10 code with age specificity that does not match the patient. The group code paired with CARC 9 determines who bears the financial responsibility — CO places it on the provider as a contractual obligation, OA indicates a coordination of benefits or other payer adjustment, PR shifts it to the patient.

Common Causes

How to Resolve

1. Review the remittance details Examine the CO-9 adjustment and any accompanying RARC codes to identify the specific reason for the denial.
2. Identify the root cause Determine which issue applies: incorrect date of birth on file, age-inappropriate diagnosis code, wrong ICD-10 code selected, among others.
3. Correct the claim Address the identified issue — update the claim data in your billing system to resolve the diagnosis inconsistent with patient age problem.
4. Resubmit the corrected claim Submit the corrected claim following the payer's resubmission guidelines. Include any supporting documentation that addresses the denial reason.
5. Appeal if the original claim was correct If the patient's age and diagnosis are both clinically accurate, appeal with documentation including DOB verification and clinical records supporting the diagnosis. Resubmission with corrected data is faster for simple errors.

Common RARC Pairings

The RARC code tells you exactly what triggered the CO-9:

How to Prevent CO-9

• Verify patient DOB at every visit
• Configure billing software to flag age-restricted diagnosis codes
• Train coders on age-specific ICD-10 code requirements
• Implement pre-submission edits for age-diagnosis validation
• Keep patient demographic data current

Also Filed As

The same CARC 9 may appear with different Group Codes:

Related Denial Codes