You must enroll in Medicare during specific windows, and missing them costs you money for life

Medicare enrollment is not automatic. You have to sign up yourself, and the government charges a penalty if you miss your important date — a penalty that stays on your monthly bill permanently. The main enrollment window is the three months before, the month of, and the three months after your 65th birthday. If you do not enroll then, you enter a different system with higher costs and longer waiting periods.

The exact important date depends on when you turn 65 and whether you are already receiving Social Security. If you are already collecting Social Security benefits, Medicare starts automatically the month you turn 65 — you do not have to do anything. If you are not yet collecting Social Security, you must enroll yourself during your Initial Enrollment Period, which runs from three months before your 65th birthday through three months after.

Key Takeaways

  • Your Initial Enrollment Period is seven months long: three months before your 65th birthday, the month you turn 65, and three months after.
  • If you are already receiving Social Security, Medicare starts automatically; if you are not, you must enroll yourself or face a permanent penalty.
  • Missing your important date triggers a late enrollment penalty that increases your Part B and Part D premiums for as long as you have Medicare.
  • You can enroll online at Medicare.gov, by phone at 1-800-MEDICARE, or in person at your local Social Security office.
  • If you are still working and have health coverage through your employer, you may have a different enrollment important date — ask your employer's benefits office.

What happens if you miss your Initial Enrollment Period

If you do not enroll during those seven months, you enter the General Enrollment Period, which runs January 1 through March 31 each year. During this window you can sign up, but your coverage does not start until July 1 of that year. That means if you miss your Initial Enrollment Period in June and do not enroll until February, you will have no Medicare coverage for five months.

More importantly, you will owe a late enrollment penalty for the rest of your life. For Part B (doctor and outpatient care), the penalty is 10 percent of the standard premium for each full year you were may be able to access but not enrolled. For Part D (prescription drug coverage), the penalty is 1 percent of the national average premium for each month you were without coverage. These penalties stack on top of your regular premiums every month, and they do not go away.

If you are still working and have employer health coverage

If you are 65 or older but still employed and covered by your employer's health plan, you do not have to enroll in Medicare during your Initial Enrollment Period. You can delay enrollment without penalty as long as you have creditable coverage — health insurance through your current employer or your spouse's current employer that is at least as good as Medicare.

When you or your spouse stops working, or when your employer coverage ends, you have eight months to enroll in Medicare without penalty. This is called your Special Enrollment Period. You will need to show proof that your employer coverage has ended — usually a letter from your employer's benefits office or your final pay stub. Ask your employer's benefits department for the exact important date and what documents to bring.

Enrolling before you turn 65

You can enroll in Medicare as early as three months before your 65th birthday. Many people do this to avoid the rush in the month they turn 65. You can enroll online at Medicare.gov, by calling 1-800-MEDICARE (1-800-633-4227), or by visiting your local Social Security office in person.

When you enroll, you will choose between Original Medicare (Part A and Part B) and Medicare Advantage (Part C). You will also decide whether to add prescription drug coverage (Part D). If you enroll online, the process takes about 10 minutes. By phone, it takes longer because the representative will walk you through each choice. Coverage typically starts the first day of the month in which you turn 65, regardless of when during that month you enroll.

Special situations that change your important date

If you are a federal employee, railroad retiree, or Native American, your enrollment rules may differ. Federal employees and railroad retirees have their own health plans and different important date. Native Americans can enroll in Medicare any month of the year without penalty, even if they miss their Initial Enrollment Period.

If you are not a U.S. citizen but are a permanent resident, you must have lived in the United States for at least five years before you can enroll in Medicare. If you are not yet a permanent resident, you cannot enroll at all. Check your immigration status with U.S. Citizenship and Immigration Services before you plan your enrollment.

How to find your exact enrollment important date

Your Initial Enrollment Period depends on your birth date. If you were born on the 1st through the 10th of any month, your Initial Enrollment Period starts three months before that month. If you were born on the 11th through the 20th, it starts two months before. If you were born on the 21st through the 31st, it starts one month before. Your period always ends three months after your birth month.

The easiest way to confirm your exact dates is to create an account at Medicare.gov and log in. Your account will show your Initial Enrollment Period and let you enroll when ready. You can also call 1-800-MEDICARE and a representative will tell you your important date over the phone.

What to have ready when you enroll

You will need your Social Security number, your date of birth, and your citizenship or immigration status. If you are enrolling by phone or in person, bring a photo ID. If you are enrolling online, you can do it without any documents in front of you — Medicare will verify your information with Social Security.

If you are delaying enrollment because you have employer coverage, gather a letter from your employer's benefits office stating that your coverage is creditable and the date it ends. Keep this letter; you will need it to prove you may have access to for a Special Enrollment Period without penalty.

Frequently Asked Questions

What if I turn 65 and I am still working?

You do not have to enroll in Medicare if your employer has 20 or more employees and you are covered by their health plan. You can wait until you retire or your coverage ends, then enroll within eight months without penalty. Tell your employer's benefits office that you are delaying Medicare so they know not to report you as uninsured.

Can I change my mind after I enroll?

Yes. You have until the end of the year in which you first enroll to switch between Original Medicare and Medicare Advantage, or to add or drop Part D. After that, you can only make changes during the Annual Enrollment Period (October 15 through December 7) or if you have a may have access to life event like losing employer coverage.

What if I already missed my important date?

You can still enroll during the General Enrollment Period (January 1 through March 31), but your coverage will not start until July 1 and you will owe a late penalty. If you have a good reason for missing your important date — serious illness, natural disaster, or a mistake by Social Security — you can ask for a waiver. Call 1-800-MEDICARE to discuss your situation.

Do I have to enroll in Part D if I do not take prescription drugs?

You do not have to enroll in Part D right now, but if you go without it and later decide you need it, you will owe a late penalty. If you are sure you will never need prescription coverage, you can skip it, but most people enroll just to avoid the penalty.

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. If you are a permanent resident, you can enroll in Medicare at 65 just like a citizen. If you are not yet a permanent resident, you cannot enroll until you are.