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Health insurance basics

Coordination of benefits

Coordination of benefits (COB) applies to the payment of health-care benefits when a member is covered by two or more benefit plans. One of the health plans will be primary and the other secondary. The primary plan pays first following its schedule of benefits; then the payments under the secondary plan are coordinated so that combined plan payments do not exceed 100 percent of covered charges. COB is sometimes called liability recovery.


  • If the employee is covered by a group contract and also by a spouse's plan, the employee's plan is primary.
  • If the employee is covered by two group contracts, the plan with the earliest effective date is considered the primary plan.


  • To determine which plan is primary for dependent children covered by more than one health plan, insurers use the birthday or gender rule.
  • If the health plans of both parents use the birthday rule, the plan of the parent whose birthday falls earlier in the year (month and day) is primary for the dependent children. If the month and day are the same, the policy that was in effect first is primary.
  • If the health plans of both parents use the gender rule, the father's plan is always primary for dependent children.
  • If the health plan of one parent uses the birthday rule and the other uses the gender rule, the gender rule prevails, and the father's plan is primary.
  • There are exceptions when a divorce decree determines which health plan is primary.