How to Update Coordination of Benefits (COB) — Guide for Parents

Last updated: October 14, 2026

If your child is covered by two commercial insurance plans, the insurance companies need to know which plan is primary and which is secondary. This is called Coordination of Benefits (COB).

If the insurance companies do not have the correct primary and secondary order on file, you may need to complete a COB update.

Why is a COB update important?

If COB is not updated and an insurance company later discovers that your child had other insurance coverage, they may recoup or take back payments they previously made.

This can happen years after a claim was originally processed. At that point, it may be too late to resubmit the claim to the correct insurance company because of timely filing requirements.

Who can update COB?

The primary policyholder is the only person who can resolve a COB issue with the insurance company.

If your child's insurance coverage is not showing the correct order, please contact both insurance companies to establish which plan should be primary and which should be secondary.

What information should you have ready?

When contacting the insurance companies, have the following information available:

  • Your child's name and date of birth

  • Member ID and group number for both insurance plans

  • The name of each insurance plan

  • Information for both policyholders

  • Any relevant divorce or separation documentation, if applicable

How is the primary insurance determined?

For two commercial plans, the following rules generally apply:

Birthday Rule

When both parents have commercial insurance covering the child, the plan belonging to the parent whose birthday (month and day) falls earlier in the calendar year is generally primary.

The year of birth does not matter.

For example:

  • Parent A's birthday: March 10

  • Parent B's birthday: August 22

  • Parent A's plan would generally be primary.

Divorce or Separation

The birthday rule does not apply in the same way when parents are divorced or separated.

  • If there is a court order stating which parent is responsible for the child's health coverage, that plan is generally primary.

  • If there is no applicable court order, the custodial parent's plan is generally primary.

If you are unsure which plan should be primary, the insurance companies can help determine the correct order based on your specific circumstances.

Contact both insurance companies

Please contact both insurance companies and make sure each has the other's insurance information on file.

Ask them to confirm:

  1. Which plan is primary.

  2. Which plan is secondary.

  3. That their records have been updated to reflect the correct order.

  4. That they have the other insurance plan's information.

  5. Obtain a call reference number at the end of the call.

Suggested script

You can use the following script when calling your insurance company:

“Hello, I am calling to establish the coordination of benefits for my child, [Child's Name], who is covered under my commercial plan, [Your Plan Name/ID], and my spouse's plan, [Spouse's Plan Name/ID]. Based on the birthday rule, [Primary Policy] should be primary. Can you confirm this and update your records to list [Primary Policy] as primary and [Secondary Policy] as secondary?”

Once the update has been completed, we recommend confirming with both insurance companies that the COB information is accurate and up to date.

Please reach out to care@finnihealth.com if you need additional guidance so we can help!