How to Enroll in Medicare Part A and Part B

When and how you enroll depends on whether you turned 65 or became disabled

Most people enroll in Medicare Part A and Part B during a seven-month window called your Initial Enrollment Period, which starts three months before the month you turn 65 and ends three months after. You can enroll online at Medicare.gov, by phone at 1-800-MEDICARE, by mail, or in person at your local Social Security office. If you miss this window, you can still enroll, but you may pay a permanent penalty on your Part B premium.

If you became disabled before 65, you are automatically enrolled in Part A and Part B 24 months after your disability benefits begin. If you are still working and have health insurance through your employer, you can delay Part B without penalty as long as you enroll within eight months of leaving that job or losing the coverage.

Part A (hospital insurance) is usually free if you or your spouse paid Medicare taxes for at least 10 years. Part B (medical insurance) has a monthly premium that changes each year. For 2024, the standard Part B premium is $164.90 per month, though it may be higher if your income was above a certain level in the prior year.

Key Takeaways

Your Initial Enrollment Period runs for seven months: three months before, the month of, and three months after your 65th birthday.
You can enroll through Medicare.gov, 1-800-MEDICARE, by mail, or at your local Social Security office.
Part A is usually free; Part B has a monthly premium that varies by income and year.
Missing your Initial Enrollment Period can result in a permanent 10% increase to your Part B premium for each year you delayed.
If you have employer health insurance while working, you can delay Part B without penalty as long as you enroll within eight months of losing that coverage.

What you need to have ready before you enroll

Gather your Social Security number, birth date, and citizenship or immigration status before you start. You will also need information about any current health insurance you have, including the name of your employer or plan if you are still covered through work. If you are enrolling by mail, you will need to fill out Form CMS-40B (process for Enrollment in Part B).

If you are explore in person or by phone, a Social Security representative or Medicare representative can walk you through the form. Having your information ready speeds up the process, whether you are enrolling online or over the phone.

Enrolling online at Medicare.gov

Go to Medicare.gov and select "Sign up for Medicare" at the top of the page. You will need to create a Medicare.gov account using your email address and a password. Once logged in, you can start your enrollment process. The online form asks for your personal information, citizenship status, and details about any current insurance coverage.

The online process typically takes 15 to 20 minutes. After you submit, you will receive a confirmation number. Medicare will mail you a notice within two weeks confirming your enrollment and telling you when your coverage begins. Most people who enroll online see their coverage start on the first day of the following month.

Enrolling by phone or in person

Call 1-800-MEDICARE (1-800-633-4227) to enroll over the phone. Representatives are available Monday through Friday, 8 a.m. to 8 p.m. Eastern time. Have your Social Security number and information about current insurance ready. The call usually takes 20 to 30 minutes. You will receive a confirmation number at the end of the call.

To enroll in person, visit your local Social Security office. 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 immigration status (such as a passport or birth certificate), and information about any current health insurance. In-person appointments often move faster than phone calls during busy times.

What happens after you enroll

Medicare will send you a Medicare card in the mail within two weeks of your enrollment. Your coverage for Part A and Part B typically begins on the first day of the month after you enroll, though it can begin on the first day of the month you turn 65 if you enroll during your Initial Enrollment Period.

You do not need to do anything else to set up your coverage. Your Medicare card will show your Medicare number, the date your coverage begins, and which parts of Medicare you have. Keep this card with you when you see a doctor or go to the hospital. If you do not receive your card within three weeks, call 1-800-MEDICARE to request a replacement.

Delaying Part B if you have employer coverage

If you are still working and have health insurance through your employer or your spouse's employer, you can delay enrolling in Part B without paying a penalty. This is called creditable coverage. You must enroll in Part B within eight months of the date you lose that employer coverage or retire, whichever comes first.

To use this exception, you need to show Medicare that your employer plan is creditable coverage. Your employer's human resources or benefits department can provide a letter stating this. Keep this letter — you will need it when you enroll in Part B later. If you miss the eight-month window, you will owe the 10% penalty for each year you delayed, and it will be added to your Part B premium permanently.

Understanding the permanent penalty for late enrollment

If you do not enroll in Part B during your Initial Enrollment Period and do not have creditable coverage through an employer, Medicare adds a 10% penalty to your Part B premium for each full year you delayed. This penalty stays on your premium for as long as you have Part B.

For example, if you turned 65 in January 2024 but did not enroll until January 2026 (two years late), your Part B premium would be 20% higher than the standard rate. The only way to avoid this penalty is to enroll during your Initial Enrollment Period or within eight months of losing employer coverage. There is no way to remove the penalty once it has been added, even if you later change your mind.

Frequently Asked Questions

Can I enroll in Part A without Part B?

Yes. Part A and Part B are separate. You can enroll in Part A only if you do not want Part B coverage. However, if you delay Part B and later change your mind, you will owe the late enrollment penalty unless you had creditable employer coverage.

What if I am still working at 65?

You can delay Part B if your employer has 20 or more employees and you are covered under their health plan. You must enroll within eight months of retiring or losing that coverage. Part A enrollment is not affected by employment status.

Do I have to pay for Part A?

Most people do not pay a premium for Part A if they or their spouse paid Medicare taxes for at least 10 years. Some people with fewer than 10 years of Medicare tax history pay a monthly premium. Medicare will tell you the amount when you enroll.

What if I miss my Initial Enrollment Period?

You can still enroll during the General Enrollment Period, which runs January 1 through March 31 each year. Coverage begins July 1. However, you will owe the 10% late penalty on your Part B premium unless you had creditable employer coverage.

How do I know if my enrollment went through?

You will receive a confirmation number when ready after enrolling online or by phone. Medicare will mail you a notice within two weeks. Your Medicare card will arrive within two to three weeks. If you do not receive these items, call 1-800-MEDICARE to confirm your enrollment status.

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.