Coordination of benefits is the process insurers use when you are covered under two or more health plans to determine which plan pays first and how much each pays. The most common scenario is when both spouses have group benefits through their respective employers — each can claim under their own plan first, then submit the remaining balance to the spouse's plan for additional reimbursement. The plan that pays first is called the primary plan, and the plan that pays second is the secondary plan. For dependent children, the "birthday rule" applies in most Canadian provinces: the parent whose birthday falls earlier in the calendar year has the primary plan for the children. Coordination of benefits can significantly reduce out-of-pocket costs but requires submitting claims to both insurers.