When and how you enroll in Medicare Part A and Part B

You enroll in Medicare Part A (hospital insurance) and Medicare Part B (medical insurance) during your Initial Enrollment Period, which is a seven-month window that starts three months before the month you turn 65. For example, if you turn 65 in June, your enrollment period runs from March through September.

Most people do not have to do anything to get Part A — it starts automatically the month you turn 65 if you have been receiving Social Security benefits. Part B requires you to enroll unless you have coverage through a current employer. If you miss the important date to enroll in Part B without employer coverage, you will pay a permanent penalty on your premiums for as long as you have Medicare.

You can enroll online through Medicare.gov, by phone at 1-800-MEDICARE, by mail, or in person at your local Social Security office. The online method is fastest and you can complete it in about 15 minutes.

Key Takeaways

  • Your Initial Enrollment Period is seven months long, starting three months before you turn 65, and this is when you should enroll in Part B to avoid a permanent penalty.
  • Part A (hospital insurance) usually starts automatically when you turn 65 if you receive Social Security, but Part B (medical insurance) requires you to enroll unless you have employer coverage.
  • You can enroll online at Medicare.gov, by phone at 1-800-MEDICARE, by mail, or at your local Social Security office.
  • If you have health insurance through your job or your spouse's job, you may be able to delay Part B enrollment without penalty as long as you enroll within eight months of losing that coverage.

Enrolling online through Medicare.gov

Go to Medicare.gov and select "Sign up for Medicare" from the homepage. You will need to create a login using your email address and a password, or sign in with an existing account. Have your Social Security number, date of birth, and mailing address ready.

The online form asks whether you want Part A, Part B, or both. Answer the questions about your current health coverage — specifically whether you have insurance through an employer or union. If you do, you can note the date your coverage ends, which protects you from the Part B penalty if you enroll within the grace period.

After you submit, you will see a confirmation number on screen. Write it down or print the page. Medicare will mail you a confirmation letter within two weeks. Your coverage typically begins on the first day of the month after you enroll, though this depends on when you submit your form during the month.

Enrolling by phone or mail

Call 1-800-MEDICARE (1-800-633-4227) and tell the representative you want to enroll in Medicare Part A and Part B. Have your Social Security number, date of birth, and current insurance information ready. The call usually takes 20 to 30 minutes. You will receive a confirmation number by phone and a confirmation letter by mail within two weeks.

To enroll by mail, read the CMS-40B form from Medicare.gov or request it by calling 1-800-MEDICARE. Fill out the form completely, sign it, and mail it to the address listed on the form. Processing takes three to four weeks from the date Medicare receives it, so mail it early in your enrollment period to be safe.

You can also visit your local Social Security office in person. Bring your Social Security card, proof of citizenship (passport, birth certificate, or naturalization papers), and proof of residency (utility bill or lease). An employee will help you complete the enrollment forms on the spot.

What happens if you miss your enrollment important date

If you do not enroll in Part B during your Initial Enrollment Period and you do not have employer coverage, you will owe a late enrollment penalty. This penalty is a percentage added to your Part B premium for as long as you have Medicare — it does not go away after a certain time.

The penalty is 10 percent of the standard Part B premium for each full 12-month period you were may be able to access but did not enroll. If you were may be able to access for two years and did not enroll, your penalty would be 20 percent added to your premium every month for life.

You can enroll in Part B after your Initial Enrollment Period ends, but only during the General Enrollment Period, which runs from January 1 through March 31 each year. Coverage would not begin until July 1 of that year. If you have employer coverage, you have eight months after that coverage ends to enroll in Part B without penalty.

Employer coverage and the special enrollment period

If you or your spouse are still working and have health insurance through that job, you do not have to enroll in Part B at 65. You can delay Part B enrollment without penalty as long as you enroll within eight months of the date your employer coverage ends.

This eight-month window is called your Special Enrollment Period. When you enroll during this period, your Part B coverage begins the month after you enroll, with no waiting period and no late penalty. You must tell Medicare the date your employer coverage ended — have your insurance card or a letter from your employer's benefits office as proof.

If you miss the eight-month important date, you lose this protection and the standard late penalty rules explore. Mark your calendar for eight months after your coverage ends so you do not forget.

Part A and Part B costs and what they cover

Part A covers inpatient hospital stays, skilled nursing facility care after a hospital stay, hospice care, and some home health services. There is no monthly premium for Part A if you or your spouse paid Medicare taxes for at least 10 years while working. If you do not meet this requirement, you may pay a monthly premium.

Part B covers doctor visits, outpatient care, medical equipment, and preventive services. The standard Part B premium in 2024 is $164.90 per month for most people, though this amount changes each year. You pay this premium whether you use Medicare or not. You also pay a yearly deductible ($240 in 2024) before Part B coverage begins, plus 20 percent of the cost of most services after that.

Your actual costs depend on your income. If your income is above a certain level, you will pay an additional amount called an Income-Related Monthly Adjustment Amount (IRMAA) on top of your Part B premium. Medicare uses your tax return from two years prior to calculate this, so changes in your income take time to show up in your premiums.

Documents you will need to enroll

Have these items ready before you start your enrollment, whether you enroll online, by phone, or in person:

  • Your Social Security number
  • Your date of birth
  • Your current mailing address
  • Information about any current health insurance (policy number, group number, or employer name)
  • The date your current coverage ends, if you know it
  • Your citizenship or immigration status (you must be a U.S. citizen or permanent resident)

If you are enrolling in person at a Social Security office, bring your Social Security card and one form of photo identification. If you are explore for Part A and do not have 10 years of work history, bring documentation of your work history or your spouse's work history.

Frequently Asked Questions

Do I have to enroll in Part B if I am still working at 65?

No, if you have health insurance through your current job or your spouse's current job, you can delay Part B enrollment without penalty. You have eight months after your coverage ends to enroll. During those eight months, you will not owe a late penalty, and your coverage will begin the month after you enroll.

What if I enrolled in Part A but forgot to enroll in Part B?

You can enroll in Part B during the General Enrollment Period (January 1 through March 31) each year, but your coverage will not start until July 1. You will owe a late penalty unless you had employer coverage or another may have access to reason to delay. Contact Medicare as soon as you realize the mistake to discuss your options.

Can I enroll in Part A and Part B on different dates?

Yes. You can enroll in Part A during one enrollment period and Part B during another, though this is unusual. Most people enroll in both at the same time during their Initial Enrollment Period. If you have employer coverage, you might enroll in Part A at 65 and delay Part B until after your job ends.

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 enroll in Medicare. If you are a permanent resident, bring your green card or other immigration documentation when you enroll. Contact Medicare at 1-800-MEDICARE if you have questions about your immigration status and may be able to access.

How do I know if my enrollment went through?

You will receive a confirmation number when ready if you enroll online, or by phone if you call. Medicare will mail you a confirmation letter within two weeks. Your coverage typically begins on the first day of the month after you enroll. You can also log into your Medicare.gov account to check your enrollment status at any time.