Health · Chapter 18 · Additional Provisions
Coordination of Benefits (COB)
Definition
Group-plan provision preventing duplicate payment/over-insurance when someone is covered by multiple group plans: the primary plan pays its full contractual benefit first, the secondary pays remaining eligible costs, and total recovery never exceeds actual allowable expenses. Spouses: each person's own employer plan is primary. Dependent children: the birthday rule — the parent whose birthday falls first in the calendar year is primary. Medicare: employer plan is primary for active workers 65+ at employers with 20+ employees; Medicare is primary for retirees, individual-policy holders, and groups under 20.
Example
$700 of allowable expenses → $700 max total, no matter how many plans cover it.
Exam tip
Birthday rule = month/day only, not who's older. And "20+ employees, still working" → group pays first, Medicare second.
Easy to confuse with
These are what this term gets tested against — if you can't tell them apart cold, drill the contrast.
Related terms