You can sign up for Medicare starting three months before the month you turn 65

Medicare enrollment opens on the first day of the three-month window before your 65th birthday month. If you turn 65 in June, you can sign up starting March 1. The enrollment period lasts until the end of the month you turn 65—so in that example, you have until June 30 to sign up without penalty.

If you miss this window, you can still sign up during the General Enrollment Period, which runs January 1 through March 31 each year. However, signing up late triggers a permanent penalty on your Part B and Part D premiums. The penalty is 10 percent of the Part B premium for each full year you delayed, and 1 percent of the Part D premium for each month you were without coverage. These penalties stay with you for life, so signing up during your initial window is worth planning for.

You do not have to wait until you turn 65 to start the process. You can contact Social Security, visit Medicare.gov, or call 1-800-MEDICARE to ask questions or gather forms as early as you want. Many people start three to four months before their birthday to avoid last-minute confusion.

Key Takeaways

  • Your initial enrollment period is the three-month window before you turn 65, the month you turn 65, and the month after—a total of seven months.
  • If you sign up during your initial period, coverage typically begins on the first day of the month you turn 65 or the first day of the following month, depending on when you enroll.
  • Missing your initial enrollment window means you pay a permanent penalty on Part B and Part D premiums for as long as you have Medicare.
  • You can sign up during the General Enrollment Period (January 1 through March 31) if you miss your initial window, but the penalty applies.
  • If you are still working and have health insurance through your employer, you may have a Special Enrollment Period that lets you delay without penalty.

When coverage actually starts depends on when you enroll

Timing matters because Medicare does not always start on the day you sign up. If you enroll during the month you turn 65, coverage begins on the first day of that month. If you enroll in the month before you turn 65, coverage starts the first day of the month you turn 65. If you enroll in the month after you turn 65, coverage begins the first day of that month.

This means if your birthday is June 15 and you enroll on June 20, your coverage starts June 1—retroactively. But if you enroll on July 5, coverage does not start until July 1. The earlier you enroll within your window, the sooner your coverage takes effect.

Special Enrollment Period if you have employer coverage

If you are still working at 65 and your employer has 20 or more employees, you may not need to sign up for Medicare right away. You can delay Part B without penalty as long as you have health insurance through your job. This is called a Special Enrollment Period.

When you do leave that job or lose the coverage, you have eight months to sign up for Part B without paying a late penalty. You must sign up within that window, or the permanent penalty applies. Part A (hospital insurance) usually has no penalty for delay if you have employer coverage, but you should still check with Social Security to confirm your specific situation.

If you are self-employed or your employer has fewer than 20 employees, you cannot use this exception. You must sign up during your initial enrollment period or face the penalty.

How to sign up: three main routes

You have three ways to enroll in Medicare. The fastest is online at Medicare.gov. You create an account, answer questions about your health history and coverage, and submit your process. Most people complete this in 15 to 20 minutes. You will need your Social Security number and information about any current health insurance.

The second route is by phone. Call 1-800-MEDICARE (1-800-633-4227). A representative will walk you through the same questions and submit your process. This takes longer—usually 30 to 45 minutes—but is helpful if you have questions or prefer not to use a computer.

The third route is in person at your local Social Security office. You can find the nearest office at ssa.gov/locator. Bring your Social Security card, proof of citizenship (passport or birth certificate), and proof of residence (utility bill or lease). In-person appointments often have wait times, so call ahead to schedule.

What happens after you sign up

After you submit your process, Social Security processes it and mails you a Medicare card within two to three weeks. Your card shows your Medicare number and which parts of Medicare you are enrolled in (usually Part A and Part B). Keep this card with you when you see doctors or go to the hospital.

At the same time, you should choose a Part D plan (prescription drug coverage) if you take medications. You can do this during your initial enrollment period or during the annual open enrollment period (October 15 through December 7). If you do not choose a plan and you do not have other drug coverage, you will owe a penalty when you eventually sign up.

You should also consider whether to enroll in a Medigap or Medicare Advantage plan. Medigap covers costs that Original Medicare does not (copays, coinsurance, deductibles). Medicare Advantage is an alternative to Original Medicare run by private insurers. You have the best rates for Medigap if you sign up within six months of your Part B start date, so this is worth deciding on early.

What to do if you missed your enrollment window

If you did not sign up during your initial enrollment period and you do not have an exception (like active employer coverage), you can still enroll during the General Enrollment Period from January 1 through March 31. Coverage will begin July 1 of that year. You will owe the late penalty on Part B and Part D for as long as you have Medicare.

If you believe you have a valid reason for missing your important date—such as a serious illness, a move to a new state, or incorrect information from Social Security—you may be able to request a Special Enrollment Period. Contact Social Security to explain your situation. They will review your case, but approval is not may provide.

Frequently Asked Questions

What if I turn 65 in January—when do I sign up?

Your enrollment period starts October 1 of the previous year. So if you turn 65 in January, you can sign up starting October 1 of the year before. Your coverage will begin January 1 if you enroll by December 31, or July 1 if you enroll during the General Enrollment Period the following year.

Can I change my mind after I sign up?

Yes. You have until the end of the month after you sign up to cancel and restart your enrollment. After that, you are locked in until the next annual open enrollment period (October 15 through December 7), unless you have a may have access to life event like moving to a new state or losing employer coverage.

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

Most people do, but you can decline Part B if you have employer coverage. You will need to sign a form saying you are turning it down. When you lose that coverage, you have eight months to sign up for Part B without penalty. If you do not, the late penalty applies.

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 years to enroll in Medicare. If you meet these requirements, you sign up the same way as anyone else. Bring proof of your immigration status (green card or naturalization certificate) when you explore.

Can I sign up before I turn 65?

You cannot enroll before your initial enrollment period begins, which is three months before the month you turn 65. However, you can contact Medicare or Social Security to ask questions, gather documents, and plan ahead. Starting early helps you avoid mistakes and ensures coverage begins on time.