Coordination of Benefits

This care may be covered by another payer per coordination of benefits (COB). The claim must be processed by the primary plan before the secondary payer considers payment.

What This Means in Behavioral Health

Patients in BH treatment often carry commercial primary plus Medicaid secondary, or two commercial policies. CO-22 appears when the wrong payer is billed first, or when primary payment information (835/EOB) is not attached to the secondary claim.

Root Causes

• Secondary claim filed before primary adjudication complete
• Primary payer not identified correctly at VOB
• Missing primary EOB on secondary institutional claim
• Birthday rule or other COB hierarchy applied incorrectly
• Medicare secondary payer (MSP) occurrence codes missing on UB-04

Prevention Tips

• Document primary/secondary sequence in VOB at admission and re-verify on insurance changes
• Hold secondary billing until primary ERA is posted
• Apply MSP occurrence and value codes on Medicare-related RTC claims when required
• Train front desk to collect all active policies, not just the card presented