You must sign up for Medicare during specific windows, or you will pay a penalty for as long as you have coverage

Medicare enrollment is not automatic. You have to sign up yourself, and the timing matters. If you miss your window, you will owe a late enrollment penalty — an extra charge added to your monthly premium that never goes away, even if you sign up years later. The penalty is calculated as a percentage of the national average premium and increases for every month you delay past your important date.

Your sign-up window depends on when you turn 65 and whether you are still working. Most people have a seven-month window centered on their 65th birthday month. If you are still covered by an employer health plan when you turn 65, your window is different and longer. The rules are strict, but they are predictable — and knowing your exact important date now means you can avoid the penalty entirely.

Key Takeaways

  • Your initial enrollment window is seven months long: three months before the month you turn 65, the month you turn 65, and three months after.
  • If you are covered by an employer health plan when you turn 65, you can delay Medicare without penalty as long as you sign up within eight months of losing that coverage.
  • Late enrollment penalties are permanent and calculated as a percentage of the national average premium for every month you miss your important date.
  • You can sign up online at Medicare.gov, by phone at 1-800-MEDICARE, or in person at your local Social Security office.
  • If you miss your initial window, you can only sign up during the general enrollment period from January 1 to March 31 each year, with coverage starting July 1.

Your seven-month initial enrollment window around age 65

If you are not covered by an employer health plan, your enrollment window opens three months before the month you turn 65 and closes three months after. For example, if you turn 65 in June, you can sign up starting in March and must sign up by September. This is called your Initial Enrollment Period, or IEP.

You should sign up as early as possible within this window — ideally in the first month it opens. Coverage does not start when ready. If you sign up in March for a June birthday, your coverage begins June 1. If you wait and sign up in August, your coverage does not start until September 1. The longer you wait, the longer you go without coverage, even though you are already in your window.

Sign up through Medicare.gov, by calling 1-800-MEDICARE, or at your local Social Security office. You will need your Social Security number, proof of citizenship or legal residency, and information about any current health coverage you have.

If you are still working and covered by employer insurance

If you are covered by a health plan through your own job or your spouse's job when you turn 65, you do not have to sign up for Medicare right away. You can delay without penalty as long as the employer plan covers at least 20 employees. This is called creditable coverage.

Your important date is eight months after your coverage ends — either when you retire, when your employer coverage stops, or when you leave the job. For example, if you turn 65 while still working and covered, and you retire at 67, you have eight months from your retirement date to sign up. If you sign up within that eight-month window, you will not owe a late penalty.

Tell your employer's benefits office that you are turning 65 and ask them to confirm in writing that your plan is creditable coverage. Keep that letter — you may need it to prove you had good reason to delay. When you do retire or lose coverage, sign up right away rather than waiting until the last month of your eight-month window.

What happens if you miss your important date

If you do not sign up during your Initial Enrollment Period and you are not protected by the employer coverage rule, you will owe a late enrollment penalty for as long as you have Medicare Part B or Part D coverage. The penalty is 10 percent of the national average Part B premium for every 12 months you were late. If you were 18 months late, you owe 15 percent extra on top of your regular premium, permanently.

The only way to avoid this penalty after you miss your window is to not sign up at all — but that means going without Medicare coverage, which leaves you uninsured and exposed to very high medical bills. That is not a realistic option for most people.

If you do miss your window, you can sign up during the general enrollment period, which runs January 1 through March 31 each year. Coverage begins July 1 of that year. This means if you miss your initial window in 2024, you can sign up during January through March 2025, but your coverage will not start until July 2025 — a gap of many months with no Medicare protection.

Special enrollment periods for life changes

If you experience certain life events, you may may have access to for a Special Enrollment Period, which gives you a window outside the normal dates. These events include losing employer coverage, moving out of your plan's service area, getting divorced, or becoming a U.S. citizen or permanent resident.

A Special Enrollment Period is usually 60 days long and starts from the date of your may have access to event. For example, if you lose employer coverage on August 15, your 60-day window runs from August 15 through October 14. If you sign up during this window, you will not owe a late penalty, even if it is years after your 65th birthday.

You must report the life event to Medicare and provide proof — such as a termination letter from your employer, a divorce decree, or a naturalization certificate. Call 1-800-MEDICARE to report the event and find out whether you may have access to for a Special Enrollment Period.

How to sign up and what to have ready

You have three ways to sign up: online at Medicare.gov, by phone at 1-800-MEDICARE (1-800-633-4227), or in person at your local Social Security office. Online is usually fastest — you can complete the process in 10 to 15 minutes and get confirmation when ready.

Before you start, gather your Social Security number, your birth date, your citizenship or legal residency documentation, and information about any health coverage you currently have (employer plan, Medicaid, TRICARE, or Veterans benefits). If you are signing up for Part D (prescription drug coverage), have a list of your current medications ready, though you can add them later.

After you submit your process, Medicare will send you a confirmation letter and your Medicare card within two to four weeks. Your coverage starts on the first day of the month you sign up, or the first day of the following month if you sign up after the 15th of the month. Check your confirmation letter to confirm your start date.

Frequently Asked Questions

What if I turn 65 while I am still working?

You can delay signing up for Medicare if your employer plan covers at least 20 employees and you are covered through your own job or your spouse's job. You have eight months after you lose that coverage to sign up without penalty. If your employer has fewer than 20 employees, you should sign up during your normal seven-month window even if you are still working.

Can I change my mind after I sign up?

Yes. You have a limited time to make changes. If you sign up during your Initial Enrollment Period, you can change your plan choice during the Annual Enrollment Period (October 15 through December 7 each year), with changes taking effect January 1. If you made a mistake on your process, call 1-800-MEDICARE to ask about correcting it.

Do I have to sign up for Part A and Part B at the same time?

No. Part A (hospital insurance) and Part B (medical insurance) have separate enrollment rules. Most people sign up for both during the same window, but you can delay Part B if you have employer coverage, while Part A enrollment is automatic for most people at 65. Talk to Medicare about your specific situation.

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

You must be a U.S. citizen or a permanent resident who has lived in the United States for at least five years to sign up for Medicare. If you are a permanent resident, you will need your green card and proof of your five-year residency. If you become a citizen or permanent resident after 65, you have eight months from that date to sign up without penalty.

Is there a penalty if I delay Part D but not Part B?

Yes. Part D (prescription drug coverage) has its own late enrollment penalty, calculated the same way as Part B. If you go 63 days or more without creditable drug coverage, you will owe an extra charge on your Part D premium for as long as you have it. If you do not take prescription drugs, you may be able to avoid this penalty by requesting an exemption from Medicare.