Which rule determines the primary plan for a dependent under coordination of benefits?

• A. The plan chosen by the employee
• B. The plan with the highest premium
• C. The parent's plan with fewer dependents
• D. The parent whose birthday falls earlier in the year

Answer: (D)

When two plans could pay for the same dependent, coordination of benefits uses a simple tie-breaker called the birthday rule. The plan of the parent whose birthday occurs earlier in the calendar year is the primary plan for the dependent. The other parent’s plan becomes secondary and pays after the primary plan, helping to prevent duplicate payments and coordinate benefits.

So, if the father’s birthday is January 5 and the mother’s birthday is June 12, the father’s plan pays first for the dependent’s medical claims. This rule isn’t about which plan has a higher premium, how many dependents there are, or which parent is older; it’s specifically about whose birthday comes first in the year.