Medicare enrollment opens on specific dates tied to your age and life events

You can enroll in Medicare during Initial Enrollment Period, which runs for seven months centered on your 65th birthday — three months before, the month you turn 65, and three months after. If you wait past this window, you will pay a permanent penalty on your Part B and Part D premiums for as long as you have Medicare, even if you enroll years later.

If you are already receiving Social Security when you turn 65, Medicare enrollment happens automatically — you do not need to do anything. If you are not yet receiving Social Security, you must contact Social Security or Medicare to enroll yourself during your Initial Enrollment Period.

Outside your Initial Enrollment Period, you can enroll during General Enrollment Period, which runs January 1 through March 31 each year. Coverage begins July 1 of that year. This route carries the penalty mentioned above, so it is slower and more expensive than enrolling on time.

Key Takeaways

  • Your Initial Enrollment Period is seven months long: three months before your 65th birthday, the month you turn 65, and three months after.
  • If you are receiving Social Security at 65, Medicare enrollment is automatic and you do not need to take action.
  • If you miss your Initial Enrollment Period, you can enroll during General Enrollment Period (January 1 through March 31 each year), but you will pay a permanent penalty on your premiums.
  • Certain life events — losing employer coverage, moving out of state, or changes in income — may open a Special Enrollment Period outside the normal windows.
  • You can enroll through Medicare.gov, by phone at 1-800-MEDICARE, or in person at your local Social Security office.

What happens if you are still working at 65

If you are covered by your employer's health plan and still working, you may not need to enroll in Medicare right away. However, the rules depend on the size of your employer. If your employer has 20 or more employees, you can delay Medicare Part B enrollment without penalty as long as you remain covered by the employer plan and actively employed.

Part A (hospital insurance) has no penalty for delay, so you can enroll whenever you want. Part D (prescription drug coverage) does carry a penalty if you go without creditable coverage for 63 days or more, so check whether your employer plan covers drugs at the same level Medicare does. If it does not, you may want to enroll in Part D even if you delay Part B.

When you leave your job or lose employer coverage, you have eight months to enroll in Part B without penalty. This is called a Special Enrollment Period. You will need to show proof that you had employer coverage — usually a letter from your employer or your insurance card.

Special Enrollment Periods for life changes

Beyond your Initial Enrollment Period and General Enrollment Period, Medicare opens enrollment windows when certain life events occur. These Special Enrollment Periods last eight months and let you enroll without the permanent penalty.

Common events that trigger a Special Enrollment Period include losing health coverage (from an employer, Medicaid, or a private plan), moving out of your Medicare Advantage plan's service area, or moving to a different state. Divorce, death of a spouse, and significant changes in income can also open a window. You must enroll within eight months of the event.

To use a Special Enrollment Period, you will need to prove the event happened. Bring documents like a termination letter from your employer, a notice from your insurance company, or a lease showing your new address. Social Security or Medicare can tell you which documents they need before you visit.

How to enroll during your window

You have three ways to enroll: online at Medicare.gov, by phone at 1-800-MEDICARE (1-800-633-4227), or in person at your local Social Security office. The online route is fastest — you can complete enrollment in about 10 minutes if you have your Social Security number and basic health information ready.

When you call, a representative will walk you through the same questions and can answer questions about which parts of Medicare you need. Wait times are usually shorter early in the week and early in the day. If you enroll in person, bring your Social Security card, proof of citizenship or legal residency (passport, birth certificate, or naturalization papers), and proof of residence (utility bill or lease).

After you enroll, Medicare mails your card within two to four weeks. You can view your coverage details online at Medicare.gov before the card arrives. Coverage typically begins the first day of the month after you enroll, though it can begin earlier if you enroll during your Initial Enrollment Period.

Penalties for missing your enrollment window

If you do not enroll in Part B during your Initial Enrollment Period and do not have a may have access to reason for the delay, you will pay a late enrollment penalty for as long as you have Medicare. The penalty is 10 percent of the standard Part B premium for each full 12-month period you were not enrolled. If you were supposed to enroll in 2024 but do not enroll until 2026, you owe two years of penalties.

Part D (prescription drug coverage) has a similar penalty: 1 percent of the national average premium for each month you went without coverage. These penalties do not go away if you enroll later — they are permanent additions to your monthly bill.

The only way to avoid the penalty is to show you had creditable coverage (coverage as good as or better than Medicare) during the time you were not enrolled. Creditable coverage includes employer plans, TRICARE, VA coverage, or certain state programs. You will need written proof from your previous insurer.

Enrollment important date for Medicare Advantage and Part D plans

Once you are enrolled in Original Medicare (Part A and Part B), you can choose a Medicare Advantage plan or add a Part D prescription drug plan. These choices have their own enrollment windows separate from your initial Medicare enrollment.

During your Initial Enrollment Period for Medicare, you can also enroll in a Medicare Advantage plan or Part D plan at the same time. After that, the main enrollment window is Annual Enrollment Period, which runs October 15 through December 7 each year. Changes take effect January 1.

If you miss Annual Enrollment Period, you can only change plans if you have a may have access to life event — losing employer coverage, moving, or changes in income. Otherwise, you are locked into your current plan for the rest of the year.

Frequently Asked Questions

Can I enroll in Medicare before I turn 65?

Your Initial Enrollment Period begins three months before your 65th birthday, so yes — you can enroll starting at age 64 and three months. If you enroll before you turn 65, your coverage will not begin until the month you turn 65. Enrolling early avoids the rush and ensures coverage starts on time.

What if I am not a U.S. citizen?

You must be a U.S. citizen or a lawful permanent resident who has lived in the United States for at least five consecutive years to enroll in Medicare. If you meet these requirements, the enrollment process is the same. Bring proof of legal residency — a green card, visa, or naturalization papers — when you enroll.

Do I have to choose between Medicare Advantage and Original Medicare right away?

No. You can enroll in Original Medicare (Part A and Part B) first, then choose a Medicare Advantage plan or add Part D coverage later during Annual Enrollment Period (October 15 through December 7) or if a may have access to life event occurs. However, if you wait past your Initial Enrollment Period to enroll in Part B, you will pay a permanent penalty.

What happens to my coverage if I move to a different state?

Your Medicare Part A and Part B coverage works in all 50 states. However, if you are in a Medicare Advantage plan, your plan may not serve your new state. Moving out of your plan's service area opens a Special Enrollment Period, giving you eight months to switch to a plan that covers your new location without penalty.

Can I enroll in Medicare if I am still working and have employer coverage?

Yes, but you may not need to enroll in Part B right away if your employer has 20 or more employees. You can delay Part B without penalty as long as you remain employed and covered. Part A has no penalty for delay. When you leave your job, you have eight months to enroll in Part B without penalty.