Which plan covers your baby?
Enter both parents' birthdays — month and day only. Result is instant.
When both parents have health insurance, the birthday rule determines which plan is primary for your newborn. Whichever parent's birthday falls earlier in the calendar year — by month and day, not birth year — their plan bills first. The other parent's plan is secondary and covers remaining costs. Coverage quality doesn't factor in — only the calendar date.
Please select a month and day for both parents before calculating.
Parent 1
Parent 2
Based on the birthday rule:
Primary — Bills First
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Secondary — Covers Remainder
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Was a claim for your baby already denied?
See exactly what to do next if the wrong insurer was billed first
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How to fix a birthday rule claim denial
1
Get the Explanation of Benefits (EOB). Request it from whichever insurer denied the claim. The denial reason should reference "coordination of benefits" or "other insurance primary." This confirms it's a birthday rule error, not a coverage issue.
2
Contact the correct primary insurer. Call the primary insurer identified above and ask them to process the claim as primary. Provide the date of service, the baby's name, and the claim number from the denial. Request a reference number for the call.
3
Ask the hospital to resubmit. Contact the hospital's billing department and explain that the claim needs to be resubmitted to the correct primary insurer. Provide the corrected insurance information. Ask them to place a hold on your account while reprocessing is pending.
4
Request secondary insurer reprocessing. Once the primary claim settles, ask the secondary insurer to reprocess the remaining balance under coordination of benefits. They may do this automatically once the primary EOB is on file.
5
File a formal appeal if resubmission is refused. If either insurer refuses to reprocess, you have the right to file a written appeal citing the coordination of benefits error. Under federal law, insurers must have an internal appeals process. If the internal appeal fails, you can escalate to your state insurance commissioner.
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Your baby's primary insurer receives the claim first and pays its share — deductibles, copays, coinsurance — per your plan's terms. The remaining balance is then sent to the secondary insurer, which may cover part or all of what's left. In the best case, dual coverage means little to no out-of-pocket cost. But this only works if claims are submitted in the correct order. A claim sent to the secondary insurer first will likely be denied — not because the service isn't covered, but because the wrong plan was billed.
When you register for delivery, the hospital will ask for both parents' insurance cards. Tell the billing staff which plan is primary and which is secondary — and confirm they have the correct order on file before your baby is admitted. This single step prevents the majority of birthday rule claim errors. If your baby has already been born, contact the hospital's billing department immediately with the corrected insurance order. The earlier you do it, the easier the resubmission process.
No. If Parent 1 has a January birthday and a high-deductible plan, and Parent 2 has a March birthday and a comprehensive plan — Parent 1's plan is still primary. The birthday rule is entirely calendar-based. There is no exception for coverage quality, and you cannot legally opt out of it. What you can do: know the rule in advance, make sure the hospital has the correct order on file, and appeal any claim denial that resulted from a coordination error.
Frequently Asked Questions
The birthday rule is an insurance coordination of benefits policy used when a child is covered under both parents' health plans. Whichever parent has a birthday earlier in the calendar year — by month and day, not birth year — their health plan becomes primary for the child. The other parent's plan is secondary. The rule applies regardless of which plan has better coverage.
When both parents share the same birthday (same month and day), the birthday rule produces a tie. Most insurers fall back to a secondary rule: whichever parent has been enrolled in their plan longer becomes primary. If enrollment dates are also identical, the insurers negotiate directly. Contact both insurers immediately to request a coordination of benefits determination so claims can be submitted correctly.
Yes — and you should. A birthday rule claim denial is a coordination of benefits error, not a coverage denial. The service is covered; it was just submitted to the wrong insurer first. You can request the correct primary insurer reprocess the claim, ask the hospital to resubmit, and formally appeal any balance that resulted from the error. BirthAppeal builds complete appeal packets for exactly this situation.
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