Medicare has three main signup periods, and missing them costs you money for life

Your first chance to sign up for Medicare is during your Initial Enrollment Period (IEP), which runs for seven calendar months. It starts three months before the month you turn 65 and ends three months after. If you turn 65 in June, your IEP runs from March through September. You must sign up during this window or face a permanent penalty on your premiums — even if you sign up years later.

If you miss your IEP, you can sign up during the General Enrollment Period (GEP), which runs January 1 through March 31 each year. Coverage starts July 1 if you sign up during this window. But signing up late means you pay a 10% penalty on your Part B premium for each full year you went without coverage. That penalty stays on your bill for as long as you have Medicare.

There is one exception: if you or your spouse had employer health coverage when you turned 65, you may have a Special Enrollment Period (SEP) that lasts eight months after that coverage ends. This route lets you sign up without the late penalty, but only if you sign up within that eight-month window.

Key Takeaways

  • Your Initial Enrollment Period is seven months long — three months before, the month of, and three months after you turn 65.
  • Missing your Initial Enrollment Period triggers a permanent 10% penalty on your Part B premium that you pay for life.
  • You can still sign up during the General Enrollment Period (January 1 through March 31), but coverage does not start until July 1 and the penalty still applies.
  • If you had employer coverage when you turned 65, you may have an eight-month Special Enrollment Period after that coverage ends, with no penalty.
  • You sign up through Medicare.gov, by phone at 1-800-MEDICARE, or in person at your local Social Security office.

Your Initial Enrollment Period: The seven-month window that matters most

The Initial Enrollment Period is the only signup window where you avoid the late penalty. It is seven calendar months total: three months before the month you turn 65, the month you turn 65 itself, and three months after.

The exact dates depend on your birthday. If you turn 65 on any day in June, your IEP runs from March 1 through September 30. If you turn 65 on any day in December, your IEP runs from September 1 through March 31 of the following year. The month of your birthday is always in the middle of the seven-month window.

You do not have to wait until the month you turn 65 to sign up. Many people sign up two or three months early, during the first part of their IEP. Coverage can start as early as the first day of the month you turn 65, even if you sign up months before.

What the late penalty costs and how long it lasts

If you miss your Initial Enrollment Period and do not have a Special Enrollment Period, you pay a permanent penalty on your Part B premium. The penalty is 10% of the standard Part B premium for each full 12-month period you did not have Part B coverage after you were first able to sign up.

The standard Part B premium changes each year. In 2024, it is $164.90 per month. A 10% penalty would add $16.49 to that monthly bill. If you go three years without signing up, the penalty is 30% — $49.47 extra per month. That penalty stays on your bill permanently, even after you finally sign up. You never get it removed, and it increases each year as the base premium increases.

The same penalty applies to Part D (prescription drug coverage) if you go without it and then sign up late. You pay 1% of the national average Part D premium for each month you were without coverage. These penalties compound: if you miss both Part B and Part D, you pay both penalties.

The General Enrollment Period: Your backup option with a catch

If you miss your Initial Enrollment Period, you can sign up during the General Enrollment Period, which runs January 1 through March 31 every year. But there are two significant catches: coverage does not start until July 1, and you still pay the late penalty.

This means if you miss your IEP in September and wait until January to sign up during the GEP, you will have no Medicare coverage for four months. During that time, you are responsible for any medical bills. When coverage finally starts on July 1, the late penalty is already applied to your first bill.

The GEP is a safety net, not a preferred route. Use it only if you missed your IEP and do not have a Special Enrollment Period available.

Special Enrollment Periods: The exception for people with employer coverage

If you or your spouse had health coverage through an employer or union when you turned 65, you may may have access to for a Special Enrollment Period. This is an eight-month window that starts the month your coverage ends, and it lets you sign up for Medicare without the late penalty.

To use a Special Enrollment Period, you must sign up within eight months of losing the employer coverage. The coverage must have been active when you turned 65 — if you left the job before turning 65, this exception does not explore. You will need to show proof of the employer coverage, usually a letter from your employer's benefits department or a copy of your insurance card.

This is the only way to avoid the late penalty if you miss your Initial Enrollment Period. If you had employer coverage and are now past your IEP, contact Medicare when ready to see if you still have time to use your Special Enrollment Period.

How to sign up before the important date

You have three ways to sign up for Medicare. The fastest is online at Medicare.gov. Go to the homepage, select "Sign up for Medicare," and follow the steps. You will need your Social Security number, date of birth, and citizenship or immigration status. The process takes about 10 minutes, and you get a confirmation number when ready.

You can also call 1-800-MEDICARE (1-800-633-4227) and speak to a representative. They can walk you through the signup process over the phone and answer questions about your specific situation. The line is open Monday through Friday, 8 a.m. to 8 p.m. Eastern time, and Saturday, 9 a.m. to 1 p.m. Eastern time.

A third option is to visit your local Social Security office in person. Bring your Social Security card, proof of citizenship or immigration status, and proof of age. You can find your nearest office at ssa.gov or by calling 1-800-772-1213. In-person signup takes longer but can be helpful if you have complex questions or need someone to walk through the process with you.

What happens after you sign up

After you sign up, Medicare sends you a confirmation letter with your Medicare number. This usually arrives within two weeks. Your coverage starts on the first day of the month you turn 65, or the first day of the month after you sign up, whichever is later.

If you sign up during your Initial Enrollment Period before you turn 65, coverage starts on the first day of the month you turn 65. If you sign up after you turn 65, coverage starts the first day of the following month. For example, if you turn 65 on June 15 and sign up on July 10, your coverage starts August 1.

You will receive your Medicare card in the mail. Keep it with you at all times. When you see a doctor or go to a hospital, show them your Medicare card. They will use the number on the card to bill Medicare for your care.

Common mistakes that trigger the late penalty

The most common mistake is waiting until after your birthday to sign up. Many people assume they can sign up anytime after they turn 65, but the important date is three months after your birthday, not three months after you turn 65. If you turn 65 on June 15, your important date is September 30, not September 15.

Another mistake is confusing Medicare with Social Security. You must sign up for Medicare separately, even if you have already signed up for Social Security. Signing up for Social Security does not automatically sign you up for Medicare. You have to do it yourself through Medicare.gov, by phone, or in person.

A third mistake is assuming your employer coverage counts as Medicare coverage. It does not. If you are still working and have health coverage through your job, you still need to sign up for Medicare during your Initial Enrollment Period or face the late penalty — unless you have a Special Enrollment Period because you will lose that coverage soon.

Frequently Asked Questions

What if I turn 65 and I am still working?

You still must sign up for Medicare during your Initial Enrollment Period, even if you have health coverage through your job. The only exception is if you work for a company with 20 or more employees and your employer coverage is primary — in that case, you may be able to delay Part B signup without penalty, but you must still sign up for Part A. Contact Medicare to confirm your situation before your important date passes.

Can I sign up for Medicare before I turn 65?

Yes. Your Initial Enrollment Period starts three months before the month you turn 65, so you can sign up as early as then. Many people sign up two or three months before their birthday to make sure coverage starts on time. You cannot sign up more than three months before your birthday.

What if I miss the important date by a few days?

Missing the important date by even one day means you miss your Initial Enrollment Period. You will have to wait until the next General Enrollment Period (January 1 through March 31) to sign up, and you will pay the late penalty. There are no exceptions for being a few days late. Sign up as soon as you know your birthday is approaching.

Do I have to sign up for Part B, or can I just take Part A?

You can sign up for Part A without Part B, but if you do not sign up for Part B during your Initial Enrollment Period, you will pay a late penalty when you do sign up later. The only way to avoid this penalty is to have a Special Enrollment Period because of employer coverage or to be covered under someone else's employer plan.

What if I am not a U.S. citizen?

You can sign up for Medicare if you are a permanent resident (green card holder) and have lived in the United States for at least five years. You must be 65 or older. Bring your green card and proof of residency when you sign up. If you are not a permanent resident, you may not be able to sign up for Medicare.