You only sign up for Medicare once, but you must act during specific windows or face penalties

You do not re-enroll in Original Medicare (Part A and Part B) every year. Once you sign up, your coverage continues automatically unless you change it. However, if you have Medicare Advantage or a prescription drug plan (Part D), you can change plans during the annual enrollment period — and if you do not actively choose a plan during that window, your current plan may change for you or you may lose coverage.

The confusion usually comes from the difference between initial enrollment (a one-time event) and the annual enrollment period (a yearly window to make changes). Missing your initial enrollment window can cost you permanently in the form of late-enrollment penalties. Missing the annual enrollment period usually just means your coverage stays the same, but it can also mean you lose access to a plan you want.

Key Takeaways

  • Original Medicare Part A and Part B require one enrollment; after that, coverage continues automatically with no annual re-enrollment needed.
  • Medicare Advantage and Part D prescription drug plans can be changed once per year during the annual enrollment period (October 15 to December 7), but you are not required to change them.
  • If you miss your initial enrollment window when you first become may be able to access, you will pay a permanent penalty on your Part B and Part D premiums for as long as you have Medicare.
  • Some life events (turning 65, losing employer coverage, moving states) create special enrollment periods outside the annual window, giving you 60 days to sign up without penalty.
  • Your plan may send you a notice that it is leaving Medicare or changing its service area; in those cases, you must choose a new plan or be automatically moved.

What happens when you first turn 65 or become may be able to access

When you turn 65, you have a seven-month window called your Initial Enrollment Period. It starts three months before the month you turn 65 and ends three months after. During this window, you can sign up for Part A and Part B without penalty. If you wait until after this window closes, you will pay a permanent 10 percent surcharge on your Part B premium for every 12 months you were may be able to access but not enrolled. The same rule applies to Part D: miss the window, and you pay a 1 percent surcharge on your premium for every month you were uninsured.

The exception is if you were covered by an employer health plan when you turned 65. In that case, you have an additional eight months after your coverage ends to sign up without penalty — this is called a Special Enrollment Period. You will need to show proof that you had employer coverage (a letter from your employer or a copy of your insurance card). If you lose that coverage and do not sign up within eight months, the penalty clock starts.

The annual enrollment period: when you can change plans

Every year from October 15 to December 7, you can change your Medicare Advantage plan, switch to Original Medicare, add or drop a Part D prescription drug plan, or change your Part D plan. This is called the Annual Enrollment Period, and it is the only time most people can make these changes. Changes take effect January 1 of the following year.

You do not have to make any changes during this window. If you do nothing, your current plan continues. However, if your plan is leaving Medicare, being discontinued in your area, or changing its service area, you will receive a notice in the mail. In those cases, you must choose a new plan, or Medicare will automatically move you to a different plan in your area — usually one with similar benefits, but not always your first choice.

When you can sign up outside the annual enrollment period

Certain life events open a Special Enrollment Period, giving you 60 days to make changes without waiting for October. These events include losing employer coverage, moving to a different state, getting married or divorced, becoming a U.S. citizen, or being released from incarceration. You will need to provide proof of the event — a termination letter from your employer, a lease or utility bill showing your new address, a marriage certificate, or a court document.

If you miss the 60-day window after a may have access to event, you will have to wait until the next annual enrollment period to make changes. Plan ahead: if you know your employer coverage is ending on a specific date, start the sign-up process before that date ends so your new Medicare coverage is in place when the old coverage stops.

What to do if you missed your initial enrollment window

If you are already past your Initial Enrollment Period and did not sign up, you can still enroll in Part A and Part B, but you will owe the late-enrollment penalty for as long as you have Medicare. The penalty is 10 percent of the standard Part B premium for every 12 months you were may be able to access but not enrolled. If you were may be able to access for eight years and did not sign up, you would pay a 70 percent surcharge on top of your regular premium — permanently.

The only way to avoid or reduce this penalty is to show that you had creditable coverage (employer insurance or retiree coverage) during the time you were not enrolled in Medicare. You will need to contact Social Security with proof of that coverage. If you can document it, the penalty may be waived or reduced. If you cannot, you will owe the full penalty.

Medicare Advantage and Part D: what changes and what stays the same

If you have a Medicare Advantage plan or a standalone Part D prescription drug plan, you can change plans every year during the annual enrollment period. You can also switch from Medicare Advantage back to Original Medicare, or from Original Medicare to Medicare Advantage. These changes take effect January 1.

If you do nothing during the annual enrollment period, your current plan continues into the next year — unless your plan is leaving Medicare or your area. In that case, you will be notified and must choose a new plan. Some plans also change their formularies (the list of covered drugs) or their provider networks every year, so even if you keep the same plan, your out-of-pocket costs or covered doctors may change. Review your plan's annual notice of changes, usually sent in September, to see if the changes affect you.

How to stay on track with enrollment important date

Mark October 15 on your calendar every year. That is when the annual enrollment period opens. You do not have to act — your coverage will continue if you do nothing — but it is a good time to review your current plan and see if a different one would save you money or give you better access to your doctors.

If you have a life event (job loss, move, marriage, divorce), contact Medicare or Social Security within 60 days. Do not wait for the annual enrollment period. A Special Enrollment Period gives you the same rights to change plans, and it keeps you from accidentally going uninsured. Keep copies of any documents that prove the event — termination letters, lease agreements, court orders — because you will need them to show you may have access to for the special window.

Frequently Asked Questions

What happens if I do not sign up for Medicare at 65?

You can still sign up later, but you will pay a permanent penalty on your Part B and Part D premiums for every month you were may be able to access but not enrolled. The only exception is if you had employer coverage during that time; in that case, bring proof to Social Security and the penalty may be waived.

Can I change my Medicare plan in January?

No. The annual enrollment period closes December 7, and changes take effect January 1. If you miss the important date, you will have to wait until October 15 of the next year to make changes — unless you have a may have access to life event that opens a Special Enrollment Period.

Do I have to change my plan every year?

No. If you are happy with your current plan and it is not leaving your area, you can keep it. Your coverage will continue automatically into the next year. You only need to act if you want to switch plans or if your plan is being discontinued.

What if my Medicare Advantage plan is leaving my area?

Medicare will send you a notice by September 30. You must choose a new plan by December 7, or Medicare will automatically assign you to a plan in your area. It is better to choose yourself, because the automatic assignment may not include your preferred doctors or pharmacies.

Can I sign up for Medicare in the middle of the year?

Only if you have a may have access to life event, such as losing employer coverage, moving states, getting married, or becoming a U.S. citizen. You will have 60 days from the event to sign up. Otherwise, you must wait for the annual enrollment period (October 15 to December 7) or your Initial Enrollment Period if you have not yet turned 65.