You must sign up during specific windows or face penalties that last for life

Medicare enrollment is not open year-round. You have set periods to sign up, and missing them costs you money — sometimes permanently. The main enrollment window is the three months before, the month of, and three months after your 65th birthday. If you wait past that window, you pay a higher premium for as long as you have Medicare, even if you sign up years later.

The other major window is the General Enrollment Period, which runs January 1 through March 31 each year. This is a second chance if you missed your birthday window, but the penalty still applies. There is also a Special Enrollment Period if you lose employer coverage or move to a new state, which gives you 60 days to sign up without penalty.

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 — sign up during this window to avoid lifetime penalties.
  • If you miss your birthday window, you can sign up during the General Enrollment Period (January 1 through March 31), but you will pay a higher premium for each year you delayed.
  • You do not need to sign up at 65 if you are still working and covered by your employer's health plan — but you must sign up within eight months of leaving that job or losing that coverage.
  • Part A (hospital insurance) and Part B (doctor visits) have separate important date and separate penalties, so missing one does not protect you from the other's penalty.
  • Social Security will contact you about three months before your 65th birthday; do not wait for them to sign you up — you must take action yourself.

Your Initial Enrollment Period: The seven-month window around your 65th birthday

Your Initial Enrollment Period starts three months before the month you turn 65 and ends three months after. This is the penalty-free window for Part A and Part B. For example, if you turn 65 in June, your window opens in March and closes in September.

You can sign up online at Medicare.gov, by phone at 1-800-MEDICARE, or in person at your local Social Security office. Online is fastest — you can complete it in about 15 minutes if you have your Social Security number and information about any current health coverage. By phone, expect to wait 30 to 45 minutes during busy times.

If you sign up during the first three months of your window (before your birthday month), coverage starts the first day of the month you turn 65. If you sign up in your birthday month or the three months after, coverage starts the first day of the following month. This timing matters if you have a gap in coverage now.

What happens if you miss your birthday window

If you do not sign up 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, and coverage will start July 1 of that year. But you will pay a late enrollment penalty on your Part B premium 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 signed up. If you were may be able to access for three years and did not sign up, you pay 30 percent more than the standard premium forever. This penalty does not go away if you sign up later or if your income changes.

Part A (hospital insurance) also has a late penalty if you do not sign up when you are first may be able to access, though the penalty is smaller and applies only if you eventually need hospital care. The penalty is 10 percent of the Part A premium for twice the number of years you were may be able to access but not signed up.

If you are still working at 65: delayed signup without penalty

You do not have to sign up for Medicare at 65 if you are covered by your employer's health plan and you or your spouse is still actively working. This is called creditable coverage. You can delay Medicare without penalty as long as you are covered.

But you must sign up within eight months of the date you lose that employer coverage or stop working, whichever comes first. If you retire in October, your eight-month window closes in June of the following year. If you wait until July, you will owe a late penalty even though you had coverage most of the time.

When you do sign up, bring documentation of your employer coverage — usually a letter from your HR department or your health plan's coverage card. Medicare uses this to confirm you had creditable coverage and to waive the penalty. Without proof, Medicare will assume you were uninsured and charge you the penalty.

Special Enrollment Periods: exceptions to the regular windows

A Special Enrollment Period gives you 60 days to sign up without penalty if you experience certain life changes. The most common reason is losing employer coverage — whether through retirement, job loss, or your employer dropping the plan. You have 60 days from the date coverage ends.

Moving to a new state also triggers a Special Enrollment Period. If you move and your current Medicare plan no longer serves your new address, you can switch plans outside the normal enrollment window. You have 60 days from the date you move.

Other may have access to events include losing Medicaid, losing TRICARE (military health coverage), or having Medicare wrongly deny your claim for coverage. Each has its own 60-day window. You will need to show proof of the event — a termination letter from your employer, a moving company receipt, or a Medicaid denial notice.

Part A and Part B have separate important date

Part A (hospital insurance) and Part B (doctor and outpatient care) enroll on the same timeline, but they are separate. You can sign up for one without the other, and missing the important date for one does not affect the other.

Most people sign up for both at the same time during their Initial Enrollment Period. But if you have employer coverage that includes hospital insurance but not doctor visits, you might delay Part B while signing up for Part A. Each has its own late penalty, so you need to track both important date.

When you sign up, Medicare will ask which parts you want. If you are unsure, ask the person helping you to explain what each part covers. It is easier to add a part during your enrollment window than to sign up late and pay a penalty.

How to sign up and what to have ready

You can sign up 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 available 24 hours a day. Phone lines are open Monday through Friday, 8 a.m. to 7 p.m. Eastern time. Social Security offices have varying hours — call ahead.

Have these documents ready: your Social Security number, your birth date, your citizenship or immigration status, and information about any current health coverage (employer plan, Medicaid, TRICARE, or Veterans benefits). If you are signing up for Part B, you will also need to confirm your income for the current year, which determines whether you pay the standard premium or a higher amount based on income.

The process takes 15 to 30 minutes online, 30 to 45 minutes by phone, and 45 minutes to an hour in person. Online is fastest and you get a confirmation number when ready. By phone or in person, you will receive a confirmation letter in the mail within two weeks.

What to ask your doctor before you sign up

Before you enroll, ask your current doctor whether they accept Medicare. Some doctors do not, and switching doctors can be disruptive. Your doctor's office can tell you in one call. If your doctor does not accept Medicare, ask them to recommend someone who does in your area.

Also ask whether your prescriptions are covered under Medicare Part D (prescription drug coverage). If you take expensive medications, the pharmacy can check this for you. If your current medications are not well covered, you may want to explore Part D plans before you sign up for Medicare, so you can choose a plan that covers them.

If you have questions about whether you need to sign up now or can delay, ask your doctor or your employer's benefits office. They can confirm whether your current coverage counts as creditable coverage under Medicare rules.

Frequently Asked Questions

What if I turn 65 and I am not a U.S. citizen?

You must be a U.S. citizen or a lawful permanent resident (green card holder) who has lived in the United States for at least five years. If you are not yet a permanent resident, you cannot sign up for Medicare. If you are a permanent resident, bring your green card when you sign up.

Can I sign up before I turn 65?

Yes. Your Initial Enrollment Period starts three months before your birthday month. You can sign up as early as that date. Signing up early does not change your coverage start date — it will still be the first of the month you turn 65 (or the following month if you sign up after your birthday month).

What if Social Security says I am already signed up?

Social Security automatically enrolls some people in Part A at 65 if they are receiving Social Security benefits. Check your Medicare status at Medicare.gov or call 1-800-MEDICARE to confirm what parts you have. If you are enrolled in Part A but not Part B, you still need to sign up for Part B during your enrollment window if you want it.

Do I have to sign up for Part D (prescription drugs) at the same time?

No. Part D has its own enrollment period: October 15 through December 7 each year. You can sign up for Part A and Part B now and sign up for Part D later during that window. But if you wait past December 7 and you do not have other creditable drug coverage, you will pay a late penalty on Part D premiums.

What if I am on Medicare now and I missed a important date years ago?

The late penalty stays with you. It does not expire or decrease over time. If you signed up three years late, you pay 30 percent more on your Part B premium for the rest of your life. The only way to avoid the penalty going forward is to make sure you do not miss any future enrollment important date.