The Three Enrollment Periods When You Can Sign Up

You can enroll in Medicare during three separate windows each year, and missing your window can cost you money for life. The first is your Initial Enrollment Period, which runs for seven months — it starts three months before the month you turn 65 and ends three months after. The second is General Enrollment Period, which runs January 1 through March 31 every year, but you pay a permanent penalty if you enroll late without a may have access to reason. The third is Special Enrollment Period, which opens only if you experience certain life events like losing employer coverage or moving to a new state.

Your birthday month matters because Medicare uses it to set your enrollment window. If you turn 65 in June, your Initial Enrollment Period runs from March through September. You do not have to enroll on your birthday itself — you can enroll any time during those seven months. However, your coverage start date depends on when you enroll: if you sign up in March, coverage begins in June; if you wait until August, coverage does not start until September.

The penalty for missing your Initial Enrollment Period is permanent. If you do not enroll in Part B (medical insurance) when you are first may be able to access, you pay an extra 10 percent for every year you were not enrolled. If you do not enroll in Part D (prescription drug coverage), you pay an extra 1 percent per month for every month you were not enrolled. These penalties stay with you for life, even if you enroll later.

Key Takeaways

  • Your Initial Enrollment Period is seven months long — three months before you turn 65, the month you turn 65, and three months after — and this is the only time you can enroll without a permanent penalty.
  • If you miss your Initial Enrollment Period, you can enroll during General Enrollment (January through March each year), but you will pay a penalty for every month you were not enrolled.
  • Your coverage start date depends on when you enroll within your window: enroll early in your period and coverage starts at the beginning of your birthday month; enroll late and coverage starts the following month.
  • You must have worked at least 10 years (40 quarters) to get Medicare Part A for free; if you have not, you can still enroll but will pay a monthly premium.
  • If you are still working and have employer health insurance, you may be able to delay enrollment without penalty if your employer has 20 or more employees.

How to Enroll and What Documents You Need

You enroll in Medicare through Social Security, either online at ssa.gov, by phone at 1-800-772-1213, or in person at your local Social Security office. You will need your Social Security number, birth certificate, proof of citizenship or legal residency (a passport or naturalization papers), and proof of income for the past year (a tax return or W-2). Have your bank account information ready if you want to set up direct deposit for any benefits.

The online process takes about 15 minutes. You create a my Social Security account, answer questions about your work history and current coverage, and choose which parts of Medicare you want. The system tells you when ready whether you may have access to for premium-free Part A and estimates what your Part B and Part D premiums will be. You receive a confirmation number on screen and by email.

If you call or visit in person, a representative walks you through the same questions and submits your enrollment on the spot. Processing takes about two weeks. You will receive your Medicare card in the mail — it used to arrive within two weeks, but Social Security now says to allow up to four weeks. If you need coverage to start on a specific date, enroll at least one month before that date.

What Happens After You Enroll

After you enroll, Social Security sends you a notice showing your enrollment decision and your coverage start date. About two weeks before your coverage begins, you receive your Medicare card in the mail. The card shows your Medicare number (which is now your Social Security number followed by a letter), which parts of Medicare you have, and the date your coverage starts.

At the same time, Medicare sends you a welcome packet with information about your coverage, a list of doctors and hospitals in your area, and details about prescription drug coverage if you enrolled in Part D. If you chose a Medicare Advantage plan (Part C) instead of Original Medicare, your plan sends you a separate welcome packet with your plan card and a list of in-network providers.

Your coverage officially starts on the first day of the month you are may be able to access, unless you enrolled late in your window — in that case, it starts the first day of the following month. You can use your Medicare card when ready once you receive it, even if your official start date has not arrived yet. Doctors and hospitals can look up your coverage using your Social Security number.

If You Are Still Working at 65

If you are still working and your employer has 20 or more employees, you can delay enrolling in Part B without penalty. This is called creditable coverage — your employer insurance is considered as good as Medicare, so you do not have to enroll when ready. You must enroll in Part A (hospital insurance) to protect yourself, but you can wait on Part B.

When you eventually leave your job or lose that coverage, you have eight months to enroll in Part B without penalty. This is called your Special Enrollment Period. You must enroll within eight months or you will pay the permanent late-enrollment penalty. Contact Social Security as soon as your employer coverage ends to start this clock.

If your employer has fewer than 20 employees, the rules are different — you must enroll in Medicare when you turn 65, even if you are still working. Your employer insurance becomes secondary to Medicare. Check with your employer's benefits department about your company size if you are unsure.

If You Have Already Delayed Past 65

If you are older than 65 and have not yet enrolled, you can still enroll during General Enrollment Period (January 1 through March 31 each year), but you will pay a permanent penalty. The penalty for Part B is 10 percent of the standard premium for every year you were not enrolled. If the standard Part B premium is $165 per month and you waited five years, you pay an extra $82.50 per month for life.

The only way to avoid this penalty is to show that you had a may have access to reason to delay — usually that you were covered by an employer plan with 20 or more employees, or that you were a federal employee. You will need to provide proof, such as a letter from your employer confirming your coverage dates. Contact Social Security to explain your situation; they will review whether your reason qualifies.

Special Situations: Non-Citizens and Non-Workers

If you are not a U.S. citizen, you can still enroll in Medicare if you are a lawful permanent resident (green card holder) and have lived in the United States for at least five years. You will need to provide your green card and proof of residency. If you are a refugee or asylee, different rules explore — contact Social Security directly to confirm your status.

If you have not worked the required 40 quarters (10 years), you cannot get premium-free Part A. You can still enroll in Part A and pay a monthly premium, which varies based on how many quarters you did work. You can also enroll in Part B and Part D. The premium for Part A without work history is currently higher than the standard Part B premium, so confirm the exact cost before you enroll.

Common Mistakes to Avoid

The biggest mistake is waiting until after your birthday month to enroll. If you turn 65 in June and do not enroll until July, your coverage does not start until August — you have a two-month gap. Enroll during the three months before your birthday to may support coverage starts the month you turn 65.

The second mistake is assuming you are automatically enrolled. You are not. Social Security does not enroll you automatically just because you turn 65. You must contact them and complete the enrollment process yourself. If you receive Social Security retirement benefits, you may be auto-enrolled in Part A and Part B, but you should confirm this by checking your my Social Security account or calling 1-800-772-1213.

The third mistake is not enrolling in Part D (prescription drug coverage) if you take medications. If you do not enroll when you first turn 65 and later decide you need it, you pay a permanent penalty. Even if you do not take medications now, enroll anyway to avoid the penalty if your situation changes.

Frequently Asked Questions

Can I enroll in Medicare before I turn 65?

Yes, you can enroll starting three months before your 65th birthday. Your enrollment window opens on the first day of the third month before you turn 65. For example, if you turn 65 in September, you can enroll starting June 1. Enrolling early ensures your coverage starts the month you turn 65.

What if I miss my Initial Enrollment Period?

You can still enroll during General Enrollment Period (January 1 through March 31 each year), but you will pay a permanent penalty on Part B and Part D. The penalty is 10 percent per year for Part B and 1 percent per month for Part D. The only exception is if you had a may have access to reason to delay, such as employer coverage.

Does my coverage start the day I enroll?

No. Your coverage start date depends on when you enroll within your enrollment window. If you enroll in the month before your birthday month, coverage starts the first day of your birthday month. If you enroll in your birthday month or after, coverage starts the first day of the following month.

What if I am still working and have health insurance through my job?

If your employer has 20 or more employees, you can delay enrolling in Part B without penalty. You must still enroll in Part A. When you leave your job, you have eight months to enroll in Part B without penalty. If your employer has fewer than 20 employees, you must enroll in Medicare at 65 even if you are still working.

Can I change my mind after I enroll?

Yes, but only during certain windows. You can change from Original Medicare to a Medicare Advantage plan (or vice versa) during the Annual Enrollment Period (October 15 through December 7 each year). Changes take effect January 1. You can also switch plans if you have a Special Enrollment Period due to a life event like moving or losing coverage.