You must register for Medicare during your enrollment period, which begins three months before the month you turn 65

Medicare enrollment is not automatic. You have a specific window of time to sign up, and missing it can cost you money for the rest of your life. Your initial enrollment period is seven months long: it starts three months before the month you turn 65, includes the month you turn 65, and ends three months after. For example, if you turn 65 in June, your enrollment period runs from March through September.

The exact important date matters because late enrollment penalties are permanent. If you do not register during your initial seven-month window and you do not have coverage from an employer or union, Medicare will charge you a penalty on top of your monthly premium — and you will pay it every month for as long as you have Medicare. The penalty is 10 percent of the standard Part B premium for each full year you were may be able to access but not enrolled.

You do not have to wait until the month you turn 65 to sign up. In fact, signing up early — during those first three months of your enrollment period — gives you time to understand your choices and avoid rushing. Your coverage can start as early as the first day of the month you turn 65.

Key Takeaways

  • Your initial enrollment period is seven months: three months before you turn 65, the month you turn 65, and three months after.
  • If you miss your initial enrollment period and do not have employer or union coverage, you will pay a permanent 10 percent penalty on your Part B premium for every year you were late.
  • You can sign up as early as three months before your 65th birthday, and coverage can begin on the first day of the month you turn 65.
  • If you are still working and covered by your employer's health plan, you may be able to delay enrollment without penalty, but you must tell Medicare about your coverage.

What happens if you miss your initial enrollment period

If you do not sign up during your seven-month window, you enter what Medicare calls the General Enrollment Period, which runs January 1 through March 31 each year. You can sign up then, but your coverage will not start until July 1 of that year — a long wait if you miss the important date in, say, April. More importantly, you will owe the late enrollment penalty for every month you were may be able to access but not enrolled.

The penalty sticks with you. If you were may be able to access at 65 but did not sign up until age 68, you owe a penalty for 36 months of non-enrollment. That penalty is added to your monthly premium permanently — even after you turn 75, even after you have been enrolled for years. The only way to avoid it is to have had creditable coverage (employer or union health insurance) during the months you were not on Medicare.

If you are still working at 65

If you or your spouse are still working and covered by an employer or union health plan, you may not have to sign up for Medicare right at 65. This is called having creditable coverage, and it protects you from late enrollment penalties. However, you must tell Medicare that you have this coverage — straightforward having it is not enough.

You can sign up for Medicare later, during a special enrollment period that begins when your employment or coverage ends. That period lasts eight months. If you wait to sign up during this window, you will not owe a late enrollment penalty, even if you sign up years after turning 65. But you must act within those eight months after your coverage ends, or the penalty clock starts again.

To protect yourself, contact Social Security or Medicare before you retire and let them know you have employer coverage. This creates a record that you had creditable coverage, which is what Medicare will check if you sign up late.

How to sign up for Medicare

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 it in about 10 minutes if you have your Social Security number and information about any current health coverage.

If you sign up online, you will need to create a Medicare.gov account. The website will walk you through questions about your health coverage, your income (which affects what you pay), and whether you want Part A, Part B, or both. You will also choose whether you want Original Medicare or a Medicare Advantage plan, and whether you want prescription drug coverage.

If you call, a Medicare representative will ask you the same questions and can answer questions about your options. The phone line is open Monday through Friday, 8 a.m. to 7 p.m. Eastern time. If you go to a Social Security office, bring your birth certificate, proof of citizenship or legal residency, and your Social Security card.

Special cases: when you can sign up outside your initial period

Beyond the General Enrollment Period and the special enrollment period for people still working, Medicare has other windows for people in specific situations. If you are a federal employee, you have different rules. If you are on dialysis or have end-stage renal disease, you can sign up at any time. If you move out of the United States and then move back, you may have a special enrollment period.

If you think you fall into one of these categories, contact Medicare directly at 1-800-MEDICARE to ask about your options. Explaining your situation to a representative is faster and more reliable than trying to navigate the rules on your own.

What to do if you think you owe a late enrollment penalty

If you signed up for Medicare after your initial enrollment period ended and you did not have creditable coverage, you may owe a penalty. You can see what Medicare thinks you owe by logging into your Medicare.gov account or by calling 1-800-MEDICARE and asking them to review your enrollment history.

If you believe the penalty is wrong — for example, because you did have employer coverage that Medicare did not record — you can ask Medicare to reconsider. You will need to provide proof of your coverage, such as a letter from your employer's benefits department stating the dates you were covered. Send this to the address Medicare gives you when you call. The process can take several weeks, but it is worth doing if you have documentation.

Frequently Asked Questions

Can I sign up for Medicare before I turn 65?

You can sign up starting three months before the month you turn 65. For example, if your birthday is in June, you can sign up starting in March. Your coverage can begin on the first day of the month you turn 65, even if you sign up earlier.

What if I turn 65 but do not want Medicare yet?

If you have creditable coverage from an employer or union, you can delay Medicare without penalty. But you must tell Medicare about your coverage. If you do not have creditable coverage and you do not sign up, you will owe a late enrollment penalty later — even if you never use Medicare.

Do I have to sign up for both Part A and Part B?

Part A (hospital insurance) is usually free if you or your spouse paid Medicare taxes while working. Most people sign up for it automatically. Part B (doctor visits) has a monthly premium and is optional, but if you delay it without creditable coverage, you will owe a penalty. Ask Medicare about your specific situation.

What happens if I miss the important date by one day?

Missing the important date by even one day means you missed your initial enrollment period. You can still sign up during the General Enrollment Period (January through March), but your coverage will not start until July, and you will owe a late enrollment penalty unless you had creditable coverage.

How do I know my exact enrollment period dates?

Your enrollment period depends on your birth month. You can find your specific dates by logging into Medicare.gov, calling 1-800-MEDICARE, or visiting your local Social Security office. It is worth confirming your dates early so you do not accidentally miss your window.