What is the health insurance 'birthday rule'?

By Insurance.com Posted : 01/01/2011

The birthday rule is a common claims practice health insurance companies use when children are listed as dependents on two parents' group health plans. The rule helps determine which health plan is the primary policy and which is secondary so that total coverage does not exceed 100 percent of charges.

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According to the birthday rule, the primary plan belongs to the parent whose birthday falls closest to the beginning of the year. The ages of the parents are irrelevant when determining the birthday rule.  The primary plan pays out a benefit first and the secondary plan pays the remainder of the medical cost if it is a covered benefit on the secondary plan.

It’s important to remember that the "birthday rule" is not a law  -- it is simply a practice that many insurers follow. Other insurance companies do not use the birthday rule.

Here is how the birthday rule typically is modified in some other situations:

  • Same birthday. If you and your spouse share the same birthday, the policy that has provided coverage the longest becomes the primary plan.
  • COBRA vs regular health insurance. If your spouse has COBRA insurance through a prior employer and you have a health insurance plan through your current employer, your plan is the primary, regardless of the birthday rule.
  • Legally separated or divorced and not remarried. The custodial parent's plan is the primary and the noncustodial parent's plan is secondary. However, if one parent has a group plan and the other has an individual plan, the group plan becomes the primary plan.
  • Divorced and remarried. The custodial parent's plan is the primary, the stepparent's plan is secondary. If costs still remain, the noncustodial parent's plan pays last.

It's important that you read your health insurance policies carefully and work with your insurance companies to understand how benefits are coordinated. Not all plans follow the birthday rule, so it's a good idea to determine which plan is the primary and which is the secondary before you start incurring medical costs.

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2 Responses to "What is the health insurance 'birthday rule'?"
  1. Maggie Duran 24, Jul, 2012

    I have a question......8 yr old patient. Biodad has insurance and Stepdad has insurance covering Biomom and Stepdaughter. Bioparents have 50/50 custody. Does the birthday rule apply? If so, does it apply to Biomom or Stepdad? Thank You.

  2. Trish 15, Nov, 2011

    Can you get the Birthday Rule waived if it causes financial loss. Here is my situation, my husband and I both have insurance, my birthday comes first in the year so I'm the primary for our children. His insurance has a clause called a "non-duplicating" something. In essence as a secondary insurance they won't pay out anything if the primary has already covered the amount they would have covered. With this in effect I essentially get no (or very little) benefit from his insurance. My insurance on the other hand does not have a "non-duplicating" clause; therefore, if mine were the secondary for the kids then it would pay the residual amount that his doesn't pay (ie the 20% not paid by primary). Please help me with this. It seems so unfair. Why should I even keep the secondary insurance in this case. They've made a lot of money off our family premium for many years with really no benefit to us. It the "non-duplicating" clause essentially saying, "don't use us as a secondary insurance"! Thank you for your answer!


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