What is the birthday rule for health insurance?

Q: Can both parents have health insurance for a child?

Yes . There’s no law against having a child on two plans, but one plan will always be primary. However, it’s worth examining the plans, coverage, and costs to see if it’s really worth paying for both plans to have secondary coverage.

What is the birthday rule for insurance?

The birthday rule in medical billing is used by health insurance companies to decide which plan will pay first if both you and your spouse have separate health insurance plans and you have children covered by both policies. The parent whose birthday falls earlier in the calendar year has the primary plan, provided the standard birthday rule applies.

It isn’t a law, but it’s a standard practice that determines which plan is primary and which is secondary.

How does the birthday rule work?

If you and your spouse have separate health insurance plans and you have listed your kids as dependents on both plans, then the primary insurance will pay for the treatment first. And if there are still any outstanding bills, then the secondary plan will cover up to 100% of the remaining cost. Under the birthday rule, the parent born earlier in the year provides primary coverage; only the month and day matter, not the birth year.

For example, Parent A's birthday is April 10, and Parent B's birthday is September 22. Their child is covered under both parents’ health plans.

Parent A's health insurance plan pays first. The insurer processes the claim and applies the plan's deductible, copay, and coinsurance.
Parent B's health insurance plan pays second. The insurer reviews the remaining eligible expenses and applies its coverage rules.
The parents pay any remaining costs. If neither plan covers the full bill, the family is responsible for the balance.

If you and your spouse have the same birthday, the plan that’s been in place longer is primary.

Are there exceptions to the birthday rule?

Yes. The birthday rule does not apply to every family or health insurance plan. The main one to remember is that a court order will always override the birthday rule.

Here are a few other situations to consider.

Situation	Does the birthday rule apply?
Parents are divorced or legally separated	Depends on the custody arrangement
Custodial parent remarries	No
One parent has COBRA	No
Newborn	Yes
Young adult with parents’ and spouse’s insurance	No

Legally separated or divorced

If you’re legally separated or divorced and not remarried, the person with primary custody provides primary healthcare coverage for dependents. With joint custody, the birthday rule applies.

However, this stipulation only applies if a group plan covers both parents. If the parent with primary custody has an individual plan and the non-custodial parent has a group plan, the non-custodial parent’s health plan is primary.

Custodial parent is remarried

If you remarry, coverage works like this:

Your plan provides primary coverage
Your new spouse’s plan provides secondary coverage
Your ex-spouse’s plan fills any remaining coverage gaps

One parent has COBRA insurance

If you have COBRA and an employer-sponsored group health plan covers your current or former spouse, that carrier provides primary coverage. COBRA insurance offers continuation coverage that’s more expensive than a health plan offered through work for an active employee.

For a newborn

When a baby is born, the mother’s insurance will cover the delivery and related costs. A newborn is automatically covered under the parents’ policy for 30 days, after which they need to be added. When each parent has their own policy, the birthday rule will apply.

A young adult is covered under a parent’s and spouse’s plan

When a young adult has health insurance through both a parent and a spouse, the birthday rule does not determine which plan pays first. Instead, the plan that has covered the young adult the longest will be primary. A young adult can stay on a parent’s plan until age 26.

Do all health plans follow the birthday rule?

No. The birthday rule is a common insurance practice, but rules for determining primary coverage vary by plan type and situation. Review both policies' coordination-of-benefits provisions and contact the insurers to confirm which plan pays first.

This means it's essential that you read your health insurance policies carefully and work with your insurance companies to understand how the insurer coordinates benefits. It's a good idea to determine which plan is primary before you start incurring medical costs.

Contact your health plan if you can’t figure out how the birthday rule affects your insurance and which insurer pays first.

FAQ: Health insurance birthday rule

What is coordination of benefits?

Coordination of Benefits (COB) is how two insurance companies work together to cover an insured person. The primary health plan pays the costs first, and then the secondary plan will pick up any remaining costs.

Can both parents have health insurance for a child?

Yes. There’s no law against having a child on two plans, but one plan will always be primary. However, it’s worth examining the plans, coverage, and costs to see if it’s really worth paying for both plans to have secondary coverage.

What are the pros and cons of the birthday rule?

The health insurance birthday rule is an objective way of determining which plan should be primary, making it easy to decide. However, it prevents parents from deciding for themselves which plan is best to cover their children. One plan may have better benefits or work with a provider the other doesn’t.

How can you avoid the birthday rule when it comes to insurance?

The easiest way to avoid the birthday rule is to look at both health plans and decide which is the better choice. Then, move everyone to that plan and drop coverage with the other one. Confirm that your child is enrolled in the selected plan before dropping the other coverage.