How to Add Medicare Part B to Your Coverage

You can add Medicare Part B during specific enrollment periods, or right when you first turn 65

Medicare Part B covers doctor visits, outpatient care, and medical equipment. If you did not sign up for it when you first became may be able to access at 65, you can still add it later — but the timing matters, because late enrollment penalties explore if you wait too long without coverage.

The three main windows to add Part B are your Initial Enrollment Period (the seven months around your 65th birthday), the General Enrollment Period (January 1 to March 31 each year), or a Special Enrollment Period if you had employer coverage that ended. Each has different rules about when coverage starts and what penalties you might owe.

Key Takeaways

Your Initial Enrollment Period runs three months before your 65th birthday, the month you turn 65, and three months after — and this is the only window with no late penalties.
If you miss your Initial Enrollment Period and enroll during General Enrollment (January through March), coverage does not start until July 1 of that year, and you will owe a 10 percent penalty on your premium for life.
You can add Part B online through Medicare.gov, by phone at 1-800-MEDICARE, or in person at your local Social Security office.
You will need your Social Security number, birth date, and information about any current health coverage when you enroll.
If you had employer coverage when you turned 65, you may have a Special Enrollment Period that lets you add Part B without penalties, even years later.

Your Initial Enrollment Period: the penalty-free window

Your Initial Enrollment Period is seven months long: it starts three months before the month you turn 65 and ends three months after. During this window, you can add Part B with no late enrollment penalty, and coverage can start as early as the first day of your birth month.

This is the most important enrollment window because it is the only one without penalties. If you were born in June, for example, your Initial Enrollment Period runs from March through September. You can enroll anytime during those seven months, and if you enroll in March, April, or May, coverage starts June 1. If you enroll in June, July, August, or September, coverage starts the first of the following month.

If you have other health coverage — from an employer, a union, or COBRA — you can still add Part B during your Initial Enrollment Period without penalty, even if you do not use it right away. This protects you if that other coverage ends unexpectedly.

General Enrollment Period: later signup with penalties

If you miss your Initial Enrollment Period, you can still add Part B during the General Enrollment Period, which runs January 1 through March 31 every year. Coverage starts July 1 of that year, a four-month wait.

The catch is a permanent late enrollment penalty. You will pay an extra 10 percent on top of your Part B premium for as long as you have Medicare. If the standard Part B premium is $165 per month, a 10 percent penalty adds $16.50 to your bill every month for life. The penalty grows if you wait longer — two years late means 20 percent, three years means 30 percent, and so on.

The only exception is if you had creditable coverage — health insurance from an employer, union, or government program — when you turned 65 and for the months after. If that coverage ended, you may have a Special Enrollment Period instead, which avoids the penalty.

Special Enrollment Period: if your employer coverage ended

If you were covered by an employer or union health plan when you turned 65, or if you were covered as a spouse or dependent on someone else's plan, you have a Special Enrollment Period. This window lasts two months after your coverage ends, and it lets you add Part B without a late penalty, no matter how many years have passed.

To use a Special Enrollment Period, you must enroll within two months of losing that coverage. You will need to show proof that you had creditable coverage — usually a letter from your employer's benefits office or health plan stating the dates you were covered. Social Security or Medicare will ask for this proof when you enroll.

If your employer coverage ended in October, for example, you have until the end of December to enroll in Part B without penalty. Coverage will start the first of the month after you enroll, or the first of the month your employer coverage ended, whichever is later.

How to add Part B: three ways to enroll

You can add Part B online, by phone, or in person. The online method is fastest if you are comfortable with it.

Online: Go to Medicare.gov, sign in with your username and password (or create an account), and look for "Enroll in Part B" under the "Manage Your Health Coverage" section. You will answer questions about your current coverage and birth date. The system will tell you right away when your coverage can start.

By phone: Call 1-800-MEDICARE (1-800-633-4227). A representative will walk you through the enrollment questions. The call usually takes 10 to 15 minutes. Have your Social Security number and birth date ready.

In person: Visit your local Social Security office. You can find the nearest one at ssa.gov or by calling 1-800-772-1213. Bring your Social Security card, proof of citizenship or legal residency, and proof of any current health coverage. No appointment is needed, but wait times vary.

Documents you need before you enroll

Have these items ready when you enroll, whether online, by phone, or in person:

Your Social Security number
Your date of birth
Your citizenship or legal residency status (you must be a U.S. citizen or permanent resident)
Information about any current health coverage (employer plan, COBRA, retiree coverage, or other Medicare coverage)
If using a Special Enrollment Period: a letter from your employer or health plan showing the dates you were covered

If you are enrolling by phone or in person and you had employer coverage, bring the letter proving it. If you are enrolling online, you can upload it or mail it to Medicare afterward — the system will tell you where to send it.

What happens after you enroll

After you submit your enrollment, Medicare will send you a confirmation letter within two weeks. This letter states your coverage start date and your monthly premium amount. Keep this letter for your records.

Your Part B coverage will start on the date stated in the letter. You do not need to do anything else — Medicare will automatically deduct your premium from your Social Security check each month, unless you ask to pay by mail or bank account instead.

If you also want prescription drug coverage (Part D) or supplemental coverage (Medigap or Medicare Advantage), you can add those separately. Part D has its own enrollment periods and penalties, and Medigap or Medicare Advantage have their own rules. But you must have Part B before you can add Part D.

Frequently Asked Questions

What if I turned 65 more than three months ago and did not sign up for Part B?

You can still add Part B during the next General Enrollment Period (January 1 through March 31), but coverage will not start until July 1, and you will owe a 10 percent lifetime penalty on your premium. If you had employer coverage when you turned 65, check whether you may have access to for a Special Enrollment Period instead, which has no penalty.

Can I add Part B if I am still working and have employer health insurance?

Yes. You can add Part B during your Initial Enrollment Period even if you have employer coverage. Many people do this to protect themselves in case the employer coverage ends. You do not have to use Part B right away — you can keep using your employer plan and switch to Medicare later.

What if I enroll in Part B but then decide I do not want it?

You can drop Part B, but only during the General Enrollment Period (January 1 through March 31). If you drop it and want to add it back later, you will owe the late enrollment penalty unless you have a Special Enrollment Period. It is usually better to keep Part B once you have it, even if you do not use it when ready.

Does my Part B premium change based on my income?

The standard Part B premium is the same for everyone, but higher-income beneficiaries pay an additional amount called an Income-Related Monthly Adjustment Amount (IRMAA). This is based on your tax return from two years before. Medicare will tell you if you owe IRMAA when you enroll or when your income changes.

Can I add Part B retroactively if I missed my enrollment period?

No. Part B coverage cannot start before the month you enroll, except during your Initial Enrollment Period, when it can start as early as your birth month. If you enroll during General Enrollment in February, coverage starts July 1 of that year — you cannot backdate it.

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.