When To Sign Up For Medicare Part B: Deadlines and Enrollment Periods

Sign up for Medicare Part B during your Initial Enrollment Period, which starts three months before the month you turn 65 and ends three months after

Your Initial Enrollment Period is a seven-month window centered on your 65th birthday month. If you turn 65 in June, your period runs from March through September. You can sign up anytime during those seven months, and coverage will begin on the first day of the month you turn 65 — or the first day of the following month if you sign up after your birthday month ends.

If you miss this window, you can still sign up during the General Enrollment Period, which runs January 1 through March 31 each year. Coverage begins July 1 of that year. However, waiting past your Initial Enrollment Period usually means paying a late enrollment penalty — a permanent increase to your Part B premium that lasts as long as you have Medicare.

The penalty is 10 percent of the standard Part B premium for each full 12-month period you could have had Part B but did not. If you delay for two years, you pay 20 percent more than the standard rate for the rest of your life. The only way to avoid this penalty is to have had creditable coverage (usually employer or union health insurance) during the time you were not enrolled.

Key Takeaways

Your Initial Enrollment Period is seven months long: three months before, the month of, and three months after you turn 65.
You can enroll anytime during your Initial Enrollment Period and coverage will start on the first of your 65th birthday month or the month after, depending on when you sign up.
If you miss your Initial Enrollment Period and do not have creditable coverage from an employer or union, you will pay a permanent penalty on your Part B premium.
The General Enrollment Period (January 1 through March 31 each year) is available to anyone, but coverage does not start until July 1 and penalties still explore if you are late.
You can sign up through Medicare.gov, by phone at 1-800-MEDICARE, or in person at your local Social Security office.

Why the timing matters: coverage gaps and penalties

Part B covers doctor visits, outpatient care, and medical equipment. If you delay signing up without creditable coverage, you create a gap in your protection. During that gap, you pay the full cost of any doctor visit or outpatient service out of pocket — Medicare does not retroactively cover those costs once you enroll.

The late enrollment penalty is separate from any coverage gap. It is a permanent surcharge added to your monthly premium. For example, if the standard Part B premium is $165 per month and you delay two years, you will pay an extra $33 per month (20 percent) for as long as you have Medicare. That adds up to thousands of dollars over time.

The only exception is if you had creditable coverage — health insurance through a current or former employer, a union, TRICARE, the Veterans Health Administration, or certain other sources — during the months you were not enrolled in Part B. If you did, you can sign up without penalty during the General Enrollment Period or even after, as long as you can document that coverage.

What counts as creditable coverage

Creditable coverage means you had health insurance that was at least as good as Medicare Part B. This includes group health plans through your own job or your spouse's job, retiree health coverage from a former employer, TRICARE (military health coverage), the Veterans Health Administration, the Federal Employees Health Benefits Program, and some state Medicaid programs.

It does NOT include Medicaid alone, supplemental insurance (Medigap), Medicare Advantage, Part D prescription drug coverage, or dental, vision, or hearing insurance. If you had only those types of coverage while you were not enrolled in Part B, you do not have creditable coverage and the penalty will explore.

If you think you have creditable coverage, bring documentation to your Social Security office or have it ready when you call 1-800-MEDICARE. You will need to show the dates your coverage was active and the name of the plan or employer.

How to sign up during your Initial Enrollment Period

You have three ways to sign up: online at Medicare.gov, by phone, or in person. The online route is fastest. Go to Medicare.gov, click "Sign up for Medicare," and follow the steps. You will need your Social Security number, date of birth, and information about any current health coverage you have.

If you prefer to call, dial 1-800-MEDICARE (1-800-633-4227). Representatives are available Monday through Friday, 8 a.m. to 8 p.m. Eastern time. Have your Social Security card and any insurance documents nearby.

You can also visit your local Social Security office in person. Find the office nearest you at ssa.gov/locator. Bring your Social Security card, proof of citizenship or legal residency, and proof of age (usually a birth certificate).

What happens if you miss your Initial Enrollment Period

If you turn 65 and do not sign up during your seven-month Initial Enrollment Period, your next chance is the General Enrollment Period from January 1 through March 31. You can sign up using the same three methods: online, by phone, or in person.

The catch is timing. If you sign up during the General Enrollment Period, your coverage does not begin until July 1 of that year. So if you miss your Initial Enrollment Period in September and do not sign up until February of the following year, you will have a gap of several months with no Part B coverage. You will also owe the late enrollment penalty unless you have creditable coverage to show.

After the General Enrollment Period ends on March 31, you cannot sign up again until the next January 1 — unless you have a Special Enrollment Period (see below). This means you could go many months without Part B coverage.

Special Enrollment Periods: exceptions to the rules

A Special Enrollment Period lets you sign up outside the normal windows without penalty if certain life events happen. These include losing employer or union coverage, losing TRICARE or VA coverage, moving out of your Medicare Advantage plan's service area, or having your employer coverage end.

You typically have two months from the date your coverage ends to sign up for Part B. The exact rules depend on what type of coverage you lost and when. If you think a life event qualifies you for a Special Enrollment Period, call 1-800-MEDICARE to confirm and sign up.

Do not assume your situation qualifies. The rules are specific, and missing the important date for a Special Enrollment Period means waiting until the next General Enrollment Period.

Coordinating Part B with Part A and other coverage

Most people turn 65 and become automatically enrolled in Part A (hospital insurance) through Social Security. Part B is separate and requires a separate enrollment decision. You do not have to take Part B just because you have Part A, but most people do because Part A alone does not cover doctor visits or outpatient care.

If you are still working and have health coverage through your job, you may be able to delay Part B without penalty — but only if your employer has 20 or more employees. This is called the working exception. If your employer has fewer than 20 employees, you should sign up for Part B when you turn 65 to avoid the penalty, even if you keep your employer coverage.

If you have a Medicare Advantage plan (Part C), you already have Part B coverage built in. You do not need to sign up separately. If you have a Medigap (supplemental) policy, you still need Part B — Medigap only works alongside Part B.

Frequently Asked Questions

What if I turn 65 but am not yet receiving Social Security?

You still need to sign up for Medicare Part B on your own. Turning 65 does not automatically enroll you in Part B the way it does for Part A. Contact Social Security or Medicare to sign up during your Initial Enrollment Period, even if you have not started collecting benefits yet.

Can I sign up for Part B before I turn 65?

Yes. Your Initial Enrollment Period begins three months before the month you turn 65. So if you turn 65 in June, you can sign up starting in March. Signing up early does not start your coverage early — it will begin on the first of your 65th birthday month or the month after, depending on when you enroll.

What if I was working and missed my Initial Enrollment Period?

If you had creditable coverage through your job, you may be able to sign up without penalty during a Special Enrollment Period. You typically have two months after your coverage ends to enroll. Call 1-800-MEDICARE to explain your situation and confirm whether you may have access to.

How much does Part B cost?

The standard Part B premium varies by year. In 2024, it is $164.90 per month for most people, though higher earners pay more. The exact amount changes each year. You can find the current premium on Medicare.gov or by calling 1-800-MEDICARE.

Do I have to take Part B if I have retiree health coverage?

You do not have to, but most people should. If your retiree coverage is creditable (as good as Medicare), you can delay Part B without penalty as long as you have that coverage. Once it ends, you have a limited time to sign up without penalty. Check with your former employer about whether your retiree plan is creditable before you decide to delay.

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.