When You Must Enroll in Medicare and When You Don't

You only enroll once, but you have limited windows to do it

No, you do not have to enroll in Medicare every year. You enroll once, and your coverage continues automatically unless you make changes. However, there are specific periods when you can enroll or change your coverage — miss these windows and you may face delays or penalties.

The key is understanding the difference between your initial enrollment (when you first become may be able to access) and your annual choices (when you can switch plans). Most people enroll once around age 65 and stay enrolled for life. But if you want to change which plan you use, you must do that during specific times of year.

Key Takeaways

You enroll in Medicare once, usually when you turn 65, and coverage continues automatically each year without re-enrolling.
Your Initial Enrollment Period is seven months long — three months before the month you turn 65, the month you turn 65, and three months after — and missing it can cost you permanently higher premiums.
If you want to change your Medicare plan, you can only do so during Annual Enrollment Period (October 15 to December 7 each year) or if you may have access to for a Special Enrollment Period.
If you delay enrolling when you are first may be able to access and do not have other may have access to coverage, you will pay a late enrollment penalty for as long as you have Medicare.
Some life changes — like losing employer coverage, moving, or getting married — open Special Enrollment Periods that let you change plans outside the normal October-December window.

Your Initial Enrollment Period: the seven-month window that matters most

When you first become may be able to access for Medicare, you have a seven-month window to enroll without penalty. This period runs for three months before the month you turn 65, the month you turn 65 itself, and three months after. For example, if you turn 65 in June, your Initial Enrollment Period runs from March through September.

During this window, you choose whether to take Original Medicare (Part A and Part B), a Medicare Advantage plan, or delay coverage if you have other insurance through an employer. The choices you make during this period set your baseline coverage. If you miss this window and do not have may have access to coverage (like an active employer health plan), you will pay a permanent penalty on your Part B and Part D premiums for every year you remain on Medicare.

The penalty is calculated as 10 percent of the standard Part B premium for each full year you delayed, and 1 percent of the standard Part D premium for each full month you delayed. These penalties do not go away — they stay on your premiums for life.

Annual Enrollment Period: your yearly chance to switch plans

Every year from October 15 through December 7, Medicare holds its Annual Enrollment Period. During these seven weeks, you can switch from one Medicare plan to another, drop coverage, or add coverage. This is the only time most people can make changes to their plan.

Changes you make during Annual Enrollment take effect on January 1 of the following year. For example, if you switch plans during the October-December 2024 window, your new plan starts on January 1, 2025. This means you need to decide and enroll before December 7 if you want the change to happen on January 1.

If you do not make any changes during Annual Enrollment, your current plan automatically renews for the next year. You do not need to do anything — your coverage straightforward continues.

Special Enrollment Periods: when you can change plans outside the normal window

Certain life events open a Special Enrollment Period, which lets you change your Medicare plan outside of the October-December window. These events include losing employer coverage, moving to a new state, getting married or divorced, having a significant drop in income, or may have access to for Medicaid.

When a may have access to event happens, you typically have 60 days to make a change. The exact rules depend on which event triggered the period. For instance, if you move to a different state, you have 60 days from the date you move to switch to a plan that works in your new location. If you lose employer coverage, you have 60 days from the date that coverage ends.

You will need to contact your Medicare plan or call Medicare directly at 1-800-MEDICARE to report the life event and request a Special Enrollment Period. Have documentation ready — such as a letter from your employer showing the end date of coverage, or a lease showing your new address.

What happens if you miss your enrollment window

If you miss your Initial Enrollment Period and do not have other may have access to coverage, you cannot enroll in Medicare until the next Annual Enrollment Period (October 15 to December 7). Your coverage will not start until January 1 of the following year, leaving you without Medicare coverage in the meantime.

More importantly, you will owe a late enrollment penalty. For Part B, this is 10 percent of the standard premium for each full year you were may be able to access but did not enroll. For Part D (prescription drug coverage), it is 1 percent of the national average Part D premium for each full month you were may be able to access but did not enroll. These penalties are permanent — they stay on your premiums for as long as you have Medicare.

The only exception is if you had other health insurance that counted as "creditable coverage" — meaning it was at least as good as Medicare. Employer plans, TRICARE, and some other group health plans may have access to. If you had creditable coverage, you can enroll without penalty when that coverage ends, as long as you enroll within 63 days.

Automatic renewal and when you need to take action

Once you are enrolled in Medicare, your coverage renews automatically every January 1. You do not need to do anything to keep your current plan active. Your premiums will be deducted from your Social Security check (or billed directly if you do not receive Social Security) without any action on your part.

However, your plan may change. Insurance companies sometimes drop plans, change service areas, or adjust benefits and costs. Before January 1 each year, your plan will send you a notice explaining any changes for the coming year. Read this notice carefully. If the changes are unacceptable, you have until December 7 to switch to a different plan during Annual Enrollment.

If you do nothing and your plan is being discontinued, Medicare will automatically move you to another plan in the same company if one exists, or to a different plan if necessary. You can then switch during Annual Enrollment if you do not like the plan Medicare chose for you.

How to enroll or make changes

To enroll in Medicare for the first time, visit Medicare.gov, call 1-800-MEDICARE, or visit your local Social Security office. You will need your Social Security number and information about any current health coverage. The process takes about 15 minutes online or over the phone.

To change your plan during Annual Enrollment or a Special Enrollment Period, you can compare plans and enroll through Medicare.gov, call 1-800-MEDICARE, or contact your current plan directly. Many plans also have enrollment specialists who can walk you through the process by phone.

Keep records of when you enroll or make changes. Save your confirmation number and the date you enrolled. If there is ever a question about your coverage start date or whether you enrolled on time, this documentation protects you.

Frequently Asked Questions

Do I have to enroll in Medicare at 65 if I am still working?

You must enroll in Part A (hospital insurance) at 65 even if you are working, or you will face a penalty. However, you may be able to delay Part B (medical insurance) if you have health insurance through your current employer and your employer has 20 or more employees. You have eight months after your employment ends or your employer coverage stops to enroll in Part B without penalty.

What if I turn 65 in the middle of the month?

Your Initial Enrollment Period is still seven months long — three months before, the month you turn 65, and three months after. The exact dates depend on your birth date. Medicare.gov has a tool that shows your specific enrollment period based on your birth month.

Can I change my mind after I enroll in a plan?

Yes, but only during Annual Enrollment (October 15 to December 7) or if you may have access to for a Special Enrollment Period. If you enroll in a plan outside these windows, you are locked in until the next Annual Enrollment Period. There is no cooling-off period or buyer's remorse exception in Medicare.

What if my plan is no longer available in my area?

If your plan is discontinued or no longer serves your area, you will receive a notice from your plan and from Medicare. You can then change plans at any time before your current plan ends, and this counts as a may have access to event for a Special Enrollment Period if needed.

Do I need to contact Medicare every year to keep my coverage active?

No. Your coverage renews automatically on January 1 each year. You do not need to call, write, or take any action to keep your Medicare active. Your premiums will continue to be deducted from your Social Security or billed directly without any action from you.

This guide is for general information only and is not medical, financial, legal, or other professional advice. For decisions specific to your situation, consult a qualified professional. See our Editorial Policy.