CO-16: Missing Information or Billing Error

What Does CO-16 Mean?

With CO (Contractual Obligation), the CARC 16 adjustment is the provider's responsibility. The payer denied or reduced payment because of incorrect date of birth, misspelled name, wrong member ID, or gender mismatch between the claim and the payer's enrollment file. 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 16 is used when the payer determines that missing information or billing error. The claim could not be processed as submitted because required information was absent, incomplete, or did not meet the payer's submission standards.

Common scenarios that trigger this adjustment include: incorrect date of birth, misspelled name, wrong member ID, or gender mismatch between the claim and the payer's enrollment file; Inactive NPI, missing PECOS enrollment, wrong taxonomy code, or ordering/referring provider not on file with the payer; Service required prior authorization but the auth number was not included on the claim, or the authorization expired before the date of service. The group code paired with CARC 16 determines who bears the financial responsibility — CO places it on the provider as a contractual obligation, PR shifts it to the patient, OA indicates a coordination of benefits or other payer adjustment.

Common Causes

How to Resolve

1. Review the remittance details Examine the CO-16 adjustment and any accompanying RARC codes to identify the specific reason for the denial.
2. Identify the root cause Determine which issue applies: missing or invalid patient demographics, invalid or missing provider NPI, missing prior authorization or referral number, among others.
3. Correct the claim Address the identified issue — update the claim data in your billing system to resolve the missing information or billing error 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 File an appeal if you believe the original claim contained all required information and the payer made a processing error. Include documentation proving the data was present on the original submission. Appeal within 120 days for Medicare or per your payer contract timeline.

Common RARC Pairings

The RARC code tells you exactly what triggered the CO-16:

How to Prevent CO-16

• Verify patient eligibility and demographics at every visit, comparing against payer records to catch mismatches before claim submission
• Implement claim scrubbing software to automatically detect missing fields, invalid codes, and data formatting errors before claims are sent
• Verify ordering and referring provider enrollment in PECOS and payer credentialing systems — a valid NPI alone is not sufficient
• Build authorization tracking workflows with expiration alerts to ensure auth numbers are captured and included on claims
• Validate diagnosis-to-procedure code alignment and ensure required modifiers are present
• Train billing staff on payer-specific requirements and common CARC 16 triggers
• Conduct monthly denial trend analysis by RARC code to identify systemic patterns and address root causes
• Use electronic claim submission to reduce manual data entry errors compared to paper claims

Also Filed As

The same CARC 16 may appear with different Group Codes:

Related Denial Codes