If we have two insurance plans, how do I know which is primary and which is secondary?

There are different rules insurance companies follow to determine who should be paying as the child’s primary insurance and who should be paying as secondary. Here are a few more popular approaches:
1. In most cases, insurance plans follow the “Birthday Rule” – The policyholder whose birthday falls first in the calendar year will have the primary insurance.
2. If the same person holds two policies, the policy that has been in effect the longest will be the primary insurance.
3. Coordination of Benefits (COB) must be completed by the subscriber of the insurance. This “questionnaire” is necessary for both insurance companies to recognize each other. If there is no COB on file for one of the insurance companies, claims will be rejected and sent to self-pay until the issue is resolved.