When a married couple or domestic partners have health coverage by way of work, they can maximize their benefits by signing their child or children up for both plans. Yet, one policy will generally be considered as primary coverage and cover health costs up to that plan's limits. The second parent's policy will be designated secondary coverage and cover the other portion of the bill to its limits. The birthday rule is one way in which many insurance companies determine which parent's health coverage plan becomes the primary plan and which becomes the secondary plan. The parent whose birthday falls first in the year will usually be considered as the primary coverage, whereas the parent whose birthday falls later in the year will be considered as the secondary insurance. Not all parents have typical insurance situations, though. If both partners were born on the same day, the parent who enjoyed the longest continuous health care coverage will be appointed the primary insurance provider. The other parent's insurer will automatically become the secondary insurance company. If the parents are divorced, the custodial parent will automatically provide primary health insurance. His or her spouse, if the child is covered under that individual's health insurance policy, will then be the second payer. If the child is not covered under that policy, then the noncustodial parent's policy will be the secondary insurer. Otherwise, the noncustodial parent's insurance provider will be the tertiary payer. The birthday rule is not a law but rather a general guideline for personal health insurance companies. Not all insurance providers follow these guidelines, or they may not follow them strictly. Also, court orders or divorce decrees may alter this arrangement. To learn more about how your insurance handles primary and secondary insurance, read your plan carefully or talk to one of our qualified insurance agents.