You must register during specific windows, or you may pay a penalty for the rest of your life

Medicare enrollment is not open year-round. You have set periods when you can sign up, and missing them costs real money. The main window is the three months before you turn 65, the month you turn 65, and the three months after — seven months total. If you miss this Initial Enrollment Period, you enter a different system with higher premiums and limited chances to fix it.

The penalty is not a one-time fee. It is a permanent percentage increase to your Part B and Part D premiums, added to every bill for as long as you have Medicare. For every 12 months you delay Part B after you turn 65, your premium goes up 10 percent. For Part D (prescription drug coverage), the penalty is roughly 1 percent of the national average premium per month of delay. These penalties stay with you even after you finally sign up.

There are exceptions — people who have health coverage through a current job, or who live outside the United States, may have different rules. But if you are a typical retiree turning 65 with no employer coverage, your seven-month window is the one that matters.

Key Takeaways

  • Your Initial Enrollment Period runs for seven months: three months before you turn 65, the month you turn 65, and three months after.
  • Missing this window triggers a permanent penalty on your Part B and Part D premiums that lasts for the rest of your life.
  • You can register online at Medicare.gov, by phone at 1-800-MEDICARE, or in person at your local Social Security office.
  • If you have health coverage through your job or a spouse's job, you may have a different enrollment important date and should contact your employer's benefits office before your 65th birthday.
  • Once you register, your coverage typically starts the first day of the month you turn 65, or the first day of the following month depending on when you sign up.

The seven-month Initial Enrollment Period

The clock starts three months before the month you turn 65. If you turn 65 in June, your enrollment period opens in March. It closes three months after the month you turn 65, so in this example it would close in September. You do not have to wait until the month you turn 65 to sign up — you can register as soon as the period opens.

Signing up early gives you time to choose your coverage and make sure everything is set before your birthday. Many people register two or three months before they turn 65 to avoid last-minute problems. If you wait until the last month of your window and something goes wrong with your process, you may not have time to fix it.

The exact dates depend on your birth month. Social Security publishes a chart on Medicare.gov showing the enrollment period for each birth month. Write down your dates or save them in your phone — this is not something to guess about.

What happens if you miss the important date

If you do not register during your Initial Enrollment Period, you enter the General Enrollment Period, which runs January 1 through March 31 each year. You can sign up then, but your coverage does not start until July 1 of that year. If you miss the important date in January and do not sign up until March, you still wait until July — a gap of four months with no coverage.

More importantly, you owe a penalty. Your Part B premium increases by 10 percent for each 12-month period you were may be able to access but not enrolled. If you were may be able to access at 65 and did not sign up until age 68, that is three years of penalties — a 30 percent increase on your Part B bill every month for the rest of your life. The same logic applies to Part D: roughly 1 percent per month of delay.

These penalties do not go away. Even if you sign up years later, the higher premium stays. The only exception is if you had creditable coverage — health insurance through an employer or a spouse's employer — during the time you were not on Medicare. If you can prove that coverage, you may avoid the penalty.

Special enrollment periods for people with employer coverage

If you or your spouse are still working and have health coverage through that job, your important date is different. You do not have to sign up for Medicare during your Initial Enrollment Period. Instead, you can wait until your employment ends or your coverage ends, whichever comes first. You then have eight months to register without a penalty — this is called a Special Enrollment Period.

The catch is that you must tell Medicare about your employer coverage. When you sign up, you will need to provide details about your job-based plan: the name of your employer, the name of the insurance company, and the dates you had coverage. If you do not report it, Medicare may assume you delayed on purpose and assess a penalty anyway.

If your spouse is the one still working, the same rule applies to you. You can delay your own enrollment as long as your spouse's coverage continues. Once your spouse retires or loses that coverage, your eight-month window opens.

How to register and what you will need

You can register three ways: 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 form in 10 to 15 minutes and get a confirmation number when ready.

Have your Social Security number ready, along with information about any health coverage you currently have. If you are registering for Part D (prescription drug coverage), have a list of your current medications or your pharmacy's name. Medicare uses this to show you which plans cover your drugs and at what cost.

You do not need to choose a specific Medicare Advantage plan or Medigap policy during registration. You register for Original Medicare (Part A and Part B) first. After that, you have time to compare and choose a supplemental plan. However, if you want Part D coverage to start on the same date as Part A and B, you should choose a plan during your Initial Enrollment Period.

When your coverage starts

If you register before the month you turn 65, your coverage typically starts on the first day of the month you turn 65. If you register during the month you turn 65, coverage usually starts the first day of the following month. If you register after the month you turn 65, coverage starts the first day of the month after you sign up.

There is one exception: if you are already receiving Social Security benefits when you turn 65, you are automatically enrolled in Part A and Part B. You do not have to do anything. Your coverage starts automatically on the first day of the month you turn 65. You will receive a Medicare card in the mail about two weeks before your birthday.

Check the confirmation you receive when you register. It will show your coverage start date. If the date is wrong, contact Medicare right away at 1-800-MEDICARE to correct it.

People who live outside the United States

If you are a U.S. citizen or permanent resident living abroad, you can still register for Medicare, but the rules are slightly different. You can register online or by phone, but you cannot register in person at a Social Security office outside the United States. Your Initial Enrollment Period is the same seven-month window, and the penalties for missing it are the same.

Part A (hospital insurance) covers you anywhere in the world. Part B (medical insurance) covers you in the United States, U.S. territories, and on ships in U.S. waters. If you live permanently outside the United States, you may not need Part B, but you should still understand the penalty rules before you decide to skip it.

What to ask your doctor and when to call Medicare

Before you turn 65, ask your doctor whether you need any specific type of coverage — for example, if you see specialists or take expensive medications, ask which Medicare plans would cover them best. Your doctor's office may have a benefits counselor who can help you understand your options.

Call Medicare at 1-800-MEDICARE if you are unsure about your enrollment important date, if you think you may have employer coverage that affects your important date, or if you have already missed your Initial Enrollment Period and want to understand your options. The call is free, and representatives can walk you through the registration process.

If you registered and your coverage start date seems wrong, or if you did not receive your Medicare card by the expected date, call Medicare to check the status. Do not wait — coverage gaps can be expensive.

Frequently Asked Questions

What if I turn 65 but I am still working and do not want Medicare yet?

You can delay Part B if you have health coverage through your job. You do not have to sign up during your Initial Enrollment Period. However, you should still sign up for Part A (hospital insurance) at 65 because it is free and has no penalty for delaying. When your job ends or your coverage ends, you have eight months to sign up for Part B without a penalty.

Can I change my mind after I register?

Yes, but only during certain windows. If you register during your Initial Enrollment Period, you can change your mind and disenroll, but only if you do it before your coverage starts. After coverage begins, you can make changes during the Annual Enrollment Period (October 15 through December 7 each year) or if you have a may have access to life event like moving or losing other coverage.

Do I have to register for Part D when I turn 65?

You do not have to, but if you do not have other prescription drug coverage and you skip Part D, you will owe a penalty when you eventually sign up. The penalty is roughly 1 percent of the national average premium for each month you were not enrolled. If you do not take any prescription medications, you may not need it, but talk to your doctor before you decide.

What if I was not a U.S. citizen until after I turned 65?

Your Initial Enrollment Period starts the month you become a citizen or permanent resident, not the month you turn 65. You have seven months from that date to register without a penalty. Contact Social Security or Medicare to confirm your enrollment important date.

If I miss my important date, can I ever get the penalty removed?

The penalty is permanent, but there are narrow exceptions. If you had creditable coverage through an employer or a spouse's employer during the time you were not on Medicare, you may be able to avoid the penalty. You will need to provide proof of that coverage. Contact Medicare to discuss your specific situation.