You must sign up for Medicare during specific windows, or you will pay a permanent penalty on your premiums

Most people become may be able to access for Medicare at age 65. You have a seven-month window called your Initial Enrollment Period to sign up: it starts three months before the month you turn 65 and ends three months after. If you sign up during this window, your coverage begins on the first day of your birth month.

If you miss this window, you can still sign up during the General Enrollment Period, which runs January 1 through March 31 each year. But coverage does not start until July 1 of that year, and you will owe a late enrollment penalty — a permanent increase to your Part B and Part D premiums that lasts as long as you have Medicare.

Some people do not have to sign up at 65 because they are still working and covered by an employer plan. If that is your situation, you have a special enrollment period after you leave that job or lose the coverage. You must sign up within eight months of losing employer coverage to avoid the penalty.

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.
  • If you sign up during your Initial Enrollment Period, Medicare Part A and Part B coverage begins on the first day of your birth month.
  • Missing your Initial Enrollment Period means waiting until the next General Enrollment Period (January through March), and your coverage will not start until July.
  • A late enrollment penalty adds permanently to your Part B and Part D premiums — the amount depends on how long you went without coverage.
  • If you are still working and covered by employer health insurance at 65, you have eight months after you leave that job to sign up without penalty.

What happens if you miss your Initial Enrollment Period

If you do not sign up during your seven-month Initial Enrollment Period, you cannot enroll in Medicare Part A or Part B until the next General Enrollment Period. That period runs January 1 through March 31 each year, no matter when you turned 65. If you miss the 2024 General Enrollment Period, you have to wait until January 2025.

When you do enroll during a General Enrollment Period, your coverage does not start right away. Part A and Part B coverage begins July 1 of that year. This means you could go without Medicare coverage for months — and you are responsible for any medical bills during that gap.

The late enrollment penalty is permanent. For Part B, 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 may be able to access but not enrolled. These penalties stay on your bill for as long as you have Medicare.

How to sign up during your Initial Enrollment Period

You can sign up for Medicare 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. You will need your Social Security number and information about any current health coverage you have.

Social Security will automatically send you a Medicare card about three months before you turn 65 if you are already receiving Social Security benefits. If you are not yet receiving benefits, you will not get a card automatically — you have to sign up yourself. The important date is still your Initial Enrollment Period, even if you have not received a card.

If you sign up online, you can complete the process in about 10 minutes. If you call or visit in person, a representative can walk you through it and answer questions about which parts of Medicare you need. Many people find it helpful to call even if they could do it online, because the representative can explain the difference between Original Medicare and Medicare Advantage plans.

Special rules if you are still working at 65

If you are still working and your employer offers health insurance, you may not need to sign up for Medicare at 65. You can delay signing up for Part B without penalty as long as your employer coverage is active. Part A (hospital insurance) has different rules — you should still sign up for Part A at 65 even if you delay Part B, because Part A is usually free and has no penalty for late enrollment.

When you leave your job or lose employer coverage, you have eight months to sign up for Part B. This is called your Special Enrollment Period. If you sign up within eight months, you will not owe a late enrollment penalty, and your coverage can start as soon as the first day of the month after you sign up.

You must be able to prove you had employer coverage. Keep a copy of your health plan documents, your insurance card, or a letter from your employer stating when your coverage ended. Medicare will ask for this proof when you sign up.

What to do if you think you already missed the important date

If you are past 65 and do not have Medicare, contact Social Security or Medicare right away. Call 1-800-MEDICARE or visit Medicare.gov to find out whether you can still enroll. In some cases, Social Security can backdate your enrollment to your Initial Enrollment Period if you have a good reason for missing it — for example, if you did not receive notice about the important date or if you were confused about whether you needed to sign up.

Social Security calls this a deemed enrollment or exceptional circumstances exception. It is not automatic, and you have to ask for it. Explain what happened and provide any documents that support your reason. Even if Social Security cannot backdate your enrollment, you can still enroll during the next General Enrollment Period and avoid further delays.

Understanding Part A and Part B enrollment separately

Medicare Part A (hospital insurance) and Part B (medical insurance) have different enrollment rules, and you can enroll in them at different times. Most people sign up for both during their Initial Enrollment Period, but you do not have to.

Part A has no late enrollment penalty. You can sign up for Part A at any time, and there is no permanent cost increase for waiting. Part B is the one with the late enrollment penalty — 10 percent of the standard premium for each year you delayed.

If you are still working at 65 and covered by employer insurance, you should sign up for Part A even if you delay Part B. Part A is usually free (you pay no monthly premium), and signing up does not affect your employer coverage. You only delay Part B if your employer plan covers medical services.

Frequently Asked Questions

What if I turn 65 in the middle of the month?

Your Initial Enrollment Period is still seven months long: three months before your birth month, your birth month itself, and three months after. If you turn 65 on June 15, your enrollment period runs from March through September. Medicare coverage begins July 1 if you sign up during this window, regardless of the exact date in June you turned 65.

Do I have to sign up for Part D at the same time as Part A and Part B?

No. Part D (prescription drug coverage) has its own enrollment period. You can sign up for Part D during your Initial Enrollment Period, but you can also wait and enroll during the annual open enrollment period (October 15 through December 7 each year). However, if you wait past your Initial Enrollment Period for Part D, you will owe a late enrollment penalty if you ever had coverage through an employer or union plan.

Can I change my mind after I sign up?

Yes, but only during certain windows. You have until March 31 of the year after you first enroll to make changes to your coverage. After that, you can make changes during the annual open enrollment period (October 15 through December 7) or if you have a may have access to life event, such as moving to a new state or losing employer coverage.

What if 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 consecutive years to sign up for Medicare. If you meet these requirements, your enrollment important date is the same as anyone else's. If you do not meet them, you are not may be able to access for Medicare.

Do I have to sign up if I am on Medicaid?

Yes. Medicaid and Medicare are separate programs. Being on Medicaid does not automatically enroll you in Medicare. You must sign up for Medicare during your Initial Enrollment Period to avoid the late enrollment penalty. Once you have Medicare, Medicaid can help pay your premiums and out-of-pocket costs.