4.3 Coordination of Benefits

Coordination of Benefits

Quick Answer: Coordination of benefits (COB) decides which plan pays first when a person is covered by two or more health plans. The primary plan pays as if there is no other coverage, the secondary plan pays remaining allowed expenses, and combined benefits can never exceed 100% of the allowed amount.

Why COB Exists

When a person is covered by two or more group health plans, Coordination of Benefits (COB) establishes the order of payment so that providers are paid in full without any plan paying more than its obligation. COB is governed by the NAIC Coordination of Benefits model regulation, which most states adopt. Without COB, two plans could each pay the full allowed amount, enriching the insured beyond the actual charge.

Primary vs. Secondary

• The primary plan pays benefits first, without considering the other coverage.
• The secondary plan pays remaining allowed expenses, up to what it would have paid as primary, so that combined payments do not exceed 100% of the allowed amount.

Order of Payment for Employees

For an employee covered under their own employer plan and a spouse's plan:

1. The plan covering the person as an employee is primary.
2. The plan covering the person as a dependent (the spouse's plan) is secondary.

The Birthday Rule for Dependent Children

For a dependent child covered under both parents' employer plans, the birthday rule determines primacy:

• The plan of the parent whose birthday falls earlier in the calendar year is primary.
• Only the month and day matter; the year of birth is irrelevant.
• If both parents have the same birthday, the plan that has covered the child longer is primary.

For divorced or separated parents, COB generally follows a specific order: the plan of the parent with financial responsibility (custodial parent) is primary, followed by the spouse of the custodial parent, then the non-custodial parent.

Non-Duplication

Under the non-duplication principle, the secondary plan is not required to duplicate benefits the primary already paid. The secondary pays only the remaining allowed expense, and total payments by primary and secondary combined cannot exceed 100% of the allowed amount.

Medicare as Primary or Secondary

When an active employee (or the employee's spouse) has both employer group health coverage and Medicare, primacy depends on employer size:

• If the employer has 20 or more employees, the employer group plan is primary and Medicare is secondary (Medicare Secondary Payer rules).
• If the employer has fewer than 20 employees, Medicare is primary.

These rules reflect the Medicare Secondary Payer (MSP) provisions and frequently appear on the A&H exam. A disabled individual under 65 with employer coverage follows similar MSP thresholds (an employer with 100 or more employees keeps the employer plan primary for a disabled worker under 65). For End-Stage Renal Disease (ESRD), Medicare is secondary to employer group coverage for a 30-month coordination period, after which Medicare becomes primary regardless of employer size. Retirees (no longer actively employed) generally find Medicare primary and any retiree health plan secondary.

How the Primary Plan Pays

The primary plan processes the claim as if no other coverage exists — it applies its own deductible, copay, coinsurance, and allowed-amount rules without regard to the secondary. The secondary plan then reviews the Explanation of Benefits (EOB) from the primary and pays the remaining allowed expense, subject to its own rules. If the primary's allowed amount fully satisfies the claim, the secondary owes nothing. If the secondary's normal benefit would have been less than the primary already paid, the secondary pays nothing — this is the non-duplication or "no balance due" principle.

Three or More Plans

When a person is covered by three or more plans, COB applies sequentially: the first plan pays as primary, the second pays the remainder as secondary, and the third pays any remaining allowed expense as tertiary. The order among multiple employer plans for one person follows the employee-vs-dependent rule, and the order for a child with three or more sources (for example, both parents plus a stepparent) follows the birthday rule among the biological/adoptive parents, then the plan of the stepparent (spouse of the custodial parent) before the non-custodial parent's spouse.

Coordination vs. Subrogation

COB is distinct from subrogation. COB arranges payment among plans that all cover the same insured; subrogation is an insurer's right to recover from a third party who caused the injury (for example, recovering medical payments from an at-fault driver's auto insurer after paying the insured's claim). The A&H exam sometimes pairs these concepts: COB orders payment, subrogation recovers it.

COB in Practice

Common exam scenarios test the order of payment directly: a working spouse covered by both their own and their spouse's plan, a child covered by two working parents, and an active employee over 65 whose employer has 25 employees. In each, the rule is mechanical — employee plan beats dependent plan, earlier birthday beats later birthday, and 20+ employees keeps the employer plan primary over Medicare. Memorize the thresholds: 20 employees for aged active workers, 100 employees for disabled active workers under 65, and 30 months for ESRD coordination.