When Medicare Starts and How to Sign Up on Time

Medicare begins the month you turn 65, but you must sign up during your enrollment window or face penalties that last for life

Your Initial Enrollment Period runs for seven months: three months before the month you turn 65, the month you turn 65, and three months after. If you sign up during this window, your coverage starts on the first day of the month you turn 65. If you miss it, your coverage starts later and your premiums go up permanently — even if you sign up years later.

The exact timing matters because Medicare has three separate enrollment periods, each with different rules and different penalties for missing the important date. Missing your Initial Enrollment Period is the most expensive mistake you can make with Medicare, because the penalty stays with you for as long as you have Part B or Part D coverage.

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 — sign up during this window to avoid permanent penalties.
If you delay Part B past your Initial Enrollment Period, your monthly premium increases by 10 percent for each year you waited, and this penalty never goes away.
If you delay Part D (prescription drug coverage) past your Initial Enrollment Period, you pay a 1 percent monthly penalty on top of your regular premium for as long as you have Part D.
You can sign up through 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 insurance through your job, you may be able to delay Part B without penalty — but you must tell Medicare about your coverage.

Your Initial Enrollment Period: The seven-month window

Your Initial Enrollment Period begins three months before the month you turn 65. For example, if you turn 65 in June, your enrollment period starts in March. It ends three months after the month you turn 65 — in this case, September. You have seven months total to sign up.

The month you turn 65 is the middle month of this window. If you sign up in that month or earlier, your Part A (hospital insurance) and Part B (medical insurance) coverage starts on the first day of the month you turn 65. If you sign up after the month you turn 65, your coverage starts the first day of the month after you sign up. This delay means you will have a gap in coverage.

Social Security automatically enrolls you in Part A and Part B when you turn 65 if you are already receiving Social Security benefits. If you are not yet receiving benefits, you must sign up yourself during your Initial Enrollment Period, or you will lose the chance to start coverage on your 65th birthday.

What happens if you miss your Initial Enrollment Period

If you do not sign up for Part B during your seven-month window, you will pay a permanent premium penalty. Your monthly Part B premium increases by 10 percent for each full year you delayed. If you waited two years, your premium goes up 20 percent. If you waited five years, it goes up 50 percent. This penalty stays with you for the rest of your life, even if you eventually sign up.

The same rule applies to Part D (prescription drug coverage). If you go without Part D coverage for more than 63 days after your Initial Enrollment Period ends, you will owe a 1 percent monthly penalty on top of your regular premium. This penalty also stays with you permanently. The penalty is calculated based on the national average Part D premium at the time you sign up, so the longer you wait, the higher the penalty becomes.

Part A (hospital insurance) does not have a late enrollment penalty, but you still need to sign up during your Initial Enrollment Period if you are not automatically enrolled through Social Security. If you wait, you may have gaps in coverage that leave you responsible for hospital bills.

General Enrollment Period: The annual sign-up window

If you miss your Initial Enrollment Period, you can sign up during the General Enrollment Period, which runs from January 1 to March 31 each year. Coverage starts July 1 of that year. This is a second chance, but it comes with the permanent penalties described above — you cannot avoid them by waiting.

The General Enrollment Period is open to anyone who missed their Initial Enrollment Period, regardless of how long ago that was. However, you will pay the late enrollment penalty for every year you were not enrolled, so signing up sooner is always cheaper than signing up later.

Special Enrollment Period: When you have a life change

A Special Enrollment Period lets you sign up outside the normal windows if you have certain life changes. The most common reason is losing health insurance through your job. If your employer coverage ends, you have two months to sign up for Medicare without penalty — even if you are younger than 65 and not yet may be able to access.

Other may have access to events include moving out of your Medicare plan's service area, losing Medicaid coverage, or having a family member become may be able to access for Medicare. If you think you have a may have access to event, contact Medicare at 1-800-MEDICARE to ask whether you can use a Special Enrollment Period. You will need to provide proof of the event, such as a letter from your employer or a notice from your insurance company.

How to sign up: Three ways to enroll

You can sign up for Medicare through Medicare.gov, the official government website. Go to the "Sign Up for Medicare" section and follow the steps. You will need your Social Security number and information about any current health insurance. The website walks you through each part of Medicare and lets you choose your coverage before you submit.

You can also call 1-800-MEDICARE (1-800-633-4227) to sign up by phone. A representative will ask you questions about your health history and current coverage, then enroll you in the parts of Medicare you choose. The phone line is open 24 hours a day, seven days a week. Wait times are usually shorter early in the morning or late in the evening.

A third option is to visit your local Social Security office in person. You can find the nearest office at ssa.gov or by calling 1-800-772-1213. Bring your Social Security card, proof of citizenship or legal residency, and proof of age. Staff can enroll you on the spot, and you will have a record of your sign-up date.

If you are still working: Delaying Part B without penalty

If you are still working and have health insurance through your job or your spouse's job, you may be able to delay Part B without paying the late enrollment penalty. This is called creditable coverage. You must tell Medicare that you have this coverage when you turn 65, even if you do not sign up for Part B yet.

To delay Part B, you sign up for Part A only during your Initial Enrollment Period. Then, when you leave your job or lose your employer coverage, you have eight months to sign up for Part B without penalty. You must be able to prove that you had employer coverage during the time you were not enrolled in Part B — your employer or insurance company can provide this proof.

Part D has different rules. If you have prescription drug coverage through your employer, you can delay Part D without penalty only if that coverage is considered creditable. Ask your employer's benefits office whether your drug coverage meets Medicare's standards. If it does, you can delay Part D. If it does not, you should sign up for Part D during your Initial Enrollment Period to avoid the permanent penalty.

Frequently Asked Questions

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

Your Initial Enrollment Period is still seven months long, and your coverage starts on the first day of the month you turn 65, regardless of which day of the month your birthday falls on. For example, if you turn 65 on June 15, your coverage starts June 1, and your enrollment period runs from March through September.

Can I change my mind after I sign up?

Yes. You have until the end of the calendar year to make changes to your coverage during your Initial Enrollment Period. After that, you can make changes only during the Annual Enrollment Period (October 15 to December 7 each year) or if you have a may have access to life event.

Do I have to sign up for all parts of Medicare at once?

No. You can sign up for Part A and Part B during your Initial Enrollment Period, then sign up for Part D later during the same period. However, waiting to sign up for Part D after your Initial Enrollment Period ends will trigger the permanent penalty, so it is better to enroll in all parts during your seven-month window.

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 to be may be able to access for Medicare at 65. If you are a permanent resident, bring your green card when you sign up. If you do not meet these requirements, you may still be able to get coverage through your state's Medicaid program.

Does my spouse have a separate enrollment period?

Yes. Each person has their own seven-month Initial Enrollment Period based on their own birth month. Your spouse's enrollment period does not depend on yours, so you each need to sign up during your own window to avoid penalties.

This guide is for general information only and is not medical, financial, legal, or other professional advice. For decisions specific to your situation, consult a qualified professional. See our Editorial Policy.