source: HealthCare.gov summary/abstract:
If a parent’s health insurance plan covers dependents, you usually can be added to their plan and stay on it until you turn 26.
How to get added to a parent’s insurance plan
Your parent can add you to their insurance during the plan’s yearly Open Enrollment Period or during a Special Enrollment Period. Your parent should check with the plan or their employer’s benefits department for details.
Plans bought through the Health Insurance Marketplace:
When a parent applies for a new plan in the Marketplace, they can include you on their application. They can add you to an existing Marketplace plan only during the yearly Open Enrollment Period or a Special Enrollment Period.
You can stay on a parent’s plan until you turn 26
Once you’re on a parent’s job-based plan, in most cases you can stay on it until you turn 26.
Generally, you can join a parent’s plan and stay on until you turn 26 even if you: –Get married
-Have or adopt a child
-Start or leave school
-Live in or out of your parent’s home
-Aren’t claimed as a tax dependent
-Turn down an offer of job-based coverage
If you’re covered by a parent’s job-based plan, your coverage usually ends when you turn 26. But check with the employer or plan. Some states and plans have different rules.
If you’re on a parent’s Marketplace plan, you can remain covered through December 31 of the year you turn 26 (or the age permitted in your state).