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

Medicare enrollment is not automatic. You have to take action during one of three enrollment windows: when you turn 65, when you first become may be able to access due to disability or end-stage renal disease, or during the general enrollment period each year. Missing your window can cost you thousands in late penalties added to your premiums — penalties that do not go away even after you finally sign up.

The most common important date is the month you turn 65. You can sign up starting three months before that birthday and ending three months after. If you miss this window, the next chance is January 1 through March 31 each year, but by then you will have already triggered a penalty. The only exception is if you or your spouse are still working and covered by an employer health plan — that coverage can delay your enrollment without penalty, but you have to report it to Medicare.

Key Takeaways

  • Sign up during the three months before your 65th birthday or the three months after — this is your main enrollment window and the only one without penalty risk.
  • If you are on disability or have end-stage renal disease, you become Medicare-may be able to access at a different age, and your enrollment window starts the same way: three months before may be able to access and three months after.
  • Employer coverage can delay your enrollment without penalty, but you must tell Medicare about it before your coverage ends.
  • Missing your window means a permanent 10 percent increase to your Part B premium and a 1 percent increase per month late for Part D prescription coverage — penalties that stay with you for life.
  • You can sign up online at Medicare.gov, by phone at 1-800-MEDICARE, or in person at your local Social Security office.

Your main enrollment window: three months before and after your 65th birthday

The Initial Enrollment Period runs for seven months total: the three calendar months before the month you turn 65, the month you turn 65, and the three calendar months after. For example, if you turn 65 in June, your window opens March 1 and closes September 30.

This is the only enrollment window without penalty consequences. If you sign up during this period, your coverage begins the first day of the month you turn 65 (or the first day of the following month if you sign up in the month you turn 65). You should sign up as early as possible within this window — waiting until September in the example above means you are uninsured for months while your process processes.

If you turn 65 and you are still working under an employer health plan, you do not have to sign up during this window. But you must tell Medicare that you have employer coverage. When your employment ends or your coverage stops, you then have eight months to sign up without penalty — this is called the Special Enrollment Period. If you do not report your employer coverage to Medicare before that eight-month window closes, you will owe late penalties even though you had coverage all along.

If you become may be able to access before 65: disability or end-stage renal disease

You become Medicare-may be able to access at any age if you have been receiving Social Security Disability Insurance (SSDI) for 24 months, or if you have end-stage renal disease (ESRD) requiring dialysis or a transplant. Your enrollment window works the same way as it does at 65: three months before your may be able to access date and three months after.

For SSDI, your may be able to access date is the first day of the 25th month of your disability payments. Social Security will tell you this date in writing. For ESRD, your may be able to access date depends on whether you are on dialysis (first day of the month you start) or have had a transplant (first day of the month of the transplant). Your nephrologist or dialysis center should tell you when to expect this date.

The same penalty rules explore: sign up during your seven-month window and you pay no penalty. Sign up after and you owe 10 percent extra on Part B for life, plus 1 percent per month late on Part D. The only exception is if you have employer coverage through your own job or a family member's job — then you get the eight-month Special Enrollment Period after that coverage ends.

The general enrollment period: January through March each year

If you miss your Initial Enrollment Period, you can sign up January 1 through March 31 each year. Coverage begins July 1 of that year. This is a long wait — you will be uninsured from the time you miss your initial window until July.

More importantly, signing up during the general enrollment period means you will owe a late penalty. Your Part B premium increases by 10 percent for each full year you were may be able to access but not signed up. This penalty is permanent — it does not go away after a few years. If you were may be able to access at 65 and do not sign up until age 68, you owe 30 percent extra on Part B for the rest of your life. Part D (prescription coverage) adds 1 percent per month of delay, also permanent.

The only people who can avoid this penalty by using the general enrollment period are those who had creditable coverage (employer coverage or retiree coverage that is at least as good as Medicare) the entire time they were may be able to access. You must be able to prove this coverage with documents from your employer or former employer.

Special enrollment periods: life changes that open enrollment outside the normal windows

Certain life changes give you a Special Enrollment Period — a window outside the normal times. These include losing employer coverage, moving out of your plan's service area, or losing Medicaid. You usually have 60 days from the event to sign up, and coverage begins the first day of the following month.

The most common special enrollment is when your employer coverage ends. If you were covered by an employer plan when you turned 65 and did not sign up for Medicare, you have eight months after that coverage ends to sign up without penalty. This is your chance to avoid the permanent late penalty — but the clock starts the day your coverage ends, not the day you realize it ended.

If you move to a different state or your Medicare Advantage plan leaves your area, you get a special enrollment period to switch plans. If you lose Medicaid, you get 60 days to sign up for Part B or Part D without penalty. Divorce also opens a special enrollment period for Part B and Part D.

How to sign up: three ways to enroll

You can sign up for Medicare online at Medicare.gov, the official government website. You will need your Social Security number and information about any current health coverage. The online process takes about 15 minutes and you get a confirmation number when ready.

You can also call 1-800-MEDICARE (1-800-633-4227) to sign up by phone. The line is open Monday through Friday, 8 a.m. to 8 p.m. Eastern time. A representative will walk you through the questions and submit your process. This takes about 20 minutes.

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 (birth certificate or passport), and proof of residency (utility bill or lease). In-person appointments usually take 30 to 45 minutes.

What happens after you sign up

After you submit your process, Medicare processes it and mails you a Medicare card within two to four weeks. Your coverage begins on the first day of the month you turn 65 (or your may be able to access date if you are under 65). Do not wait for your card to arrive — coverage is active as soon as Medicare confirms your process.

If you sign up online or by phone, you will get a confirmation number. Write it down. If you have questions about your process status, you can call 1-800-MEDICARE and give them this number.

You will also receive information about Part D (prescription drug coverage) and Medicare Advantage plans. You do not have to choose these during your Initial Enrollment Period — you can add them later during the annual open enrollment period (October 15 through December 7 each year). But if you wait, you may owe late penalties on Part D if you do not have other creditable prescription coverage.

Frequently Asked Questions

What if I miss my enrollment window by a few days?

Late is late. If your Initial Enrollment Period ends September 30 and you sign up October 1, you have missed the window and will owe a late penalty. The only exception is if you can show that Social Security or Medicare made an error in telling you your important date. Document everything — keep copies of letters, emails, and notes about calls.

Can I sign up before I turn 65 if I know I will forget?

No. You cannot sign up before your Initial Enrollment Period begins. The earliest you can sign up is the first day of the third month before you turn 65. If you are worried about forgetting, set a phone reminder or ask a family member to remind you. You can also call 1-800-MEDICARE and ask them to note your file.

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

You can sign up for Part A (hospital insurance) and Part B (medical insurance) separately, but both are part of your Initial Enrollment Period. If you delay Part B on purpose, you will owe a late penalty unless you have employer coverage. Part A usually has no late penalty if you sign up later, but it is simpler to sign up for both during your Initial Enrollment Period.

What if I am still working at 65 and my employer says I do not need Medicare?

Your employer may not require you to sign up, but you still need to tell Medicare that you have employer coverage. Do this by calling 1-800-MEDICARE or visiting Medicare.gov. When your job ends or your coverage stops, you will have eight months to sign up for Medicare without penalty. If you do not report your employer coverage first, you lose this protection.

Can I get the late penalty removed if I have a good reason for missing my important date?

Medicare rarely removes late penalties. You would need to show that Social Security or Medicare gave you wrong information in writing, or that you had a serious medical condition that prevented you from signing up. Contact your local Social Security office with documentation if you believe you have grounds for an exception.