Medicare Part B enrollment happens during specific windows, and missing your important date can cost you more in premiums for life

Medicare Part B covers doctor visits, outpatient care, and medical equipment. You enroll during your Initial Enrollment Period (the seven months surrounding your 65th birthday), during the General Enrollment Period (January 1 to March 31 each year), or during a Special Enrollment Period if you have a may have access to life event. Most people enroll through Social Security, either online at ssa.gov, by phone at 1-800-772-1213, or in person at a local Social Security office. You will need your Social Security number, birth date, and citizenship or legal residency proof.

If you miss your Initial Enrollment Period and do not have a may have access to reason, Medicare charges a late enrollment penalty — a permanent percentage increase to your Part B premium that stays with you as long as you have Medicare. The penalty is 10 percent of the standard premium for each full 12-month period you were not enrolled when you could have been. This makes timing your enrollment critical.

Key Takeaways

  • Your Initial Enrollment Period is the seven-month window centered on your 65th birthday — three months before, the month you turn 65, and three months after.
  • You can enroll through Social Security online, by phone, or in person; you do not need to contact Medicare directly.
  • If you miss your Initial Enrollment Period without a may have access to reason, you will pay a permanent penalty on top of your regular Part B premium.
  • If you were covered by an employer health plan when you turned 65, you may have a Special Enrollment Period that lets you enroll later without penalty.
  • Part B coverage begins the first day of the month after you enroll, unless you enroll during your birth month.

Understanding your enrollment windows

Your Initial Enrollment Period is seven months long: it starts three months before the month you turn 65, includes the month you turn 65, and ends three months after. For example, if you turn 65 in June, your Initial Enrollment Period runs from March through September. During this window, you can enroll without penalty, and your coverage can start as early as the first day of the month you turn 65 if you enroll in that month.

If you do not enroll during your Initial Enrollment Period, the General Enrollment Period opens every January 1 and closes March 31. You can enroll then, but your coverage will not start until July 1 of that year, and you will owe the late enrollment penalty. The penalty applies for as long as you have Medicare Part B, so delaying enrollment is expensive.

A Special Enrollment Period lets you enroll without penalty if you have a may have access to event. The most common is being covered by an employer health plan (yours or a spouse's) when you turn 65. If that applies to you, you have eight months after your employment or coverage ends to enroll without penalty. Other may have access to events include losing Medicaid, moving out of your plan's service area, or having your plan terminate. You will need to prove the may have access to event when you enroll.

How to enroll through Social Security

Social Security handles Medicare Part B enrollment for most people. You have three ways to enroll: online at ssa.gov, by phone at 1-800-772-1213 (TTY 1-800-325-0778), or in person at your local Social Security office. The online option is fastest — you can complete it in about 10 minutes if you have your information ready.

Before you contact Social Security, gather your Social Security number, birth date, and proof of U.S. citizenship or legal residency. Acceptable documents for citizenship or residency include a birth certificate, passport, naturalization certificate, or permanent resident card. You do not need to contact Medicare directly; Social Security will handle the enrollment and send your information to Medicare.

If you enroll online, you will receive a confirmation number when ready. If you enroll by phone or in person, ask for a confirmation number and the date your enrollment was processed. Keep this information in case you need to follow up. Social Security will mail you a Medicare card within two to three weeks of enrollment.

What happens after you enroll

Once Social Security processes your enrollment, Medicare Part B coverage begins on the first day of the month after you enroll — unless you enroll during the month you turn 65, in which case coverage can start the first day of that month. For example, if you enroll in August and you are not turning 65 that month, your coverage starts September 1. If you enroll in August and you turn 65 in August, your coverage can start August 1.

Your Medicare card will arrive in the mail within two to three weeks. The card shows your Medicare number, which you will use at doctor's offices and hospitals. If your card does not arrive within three weeks, contact Social Security at 1-800-772-1213 to request a replacement.

Your Part B premium is deducted from your Social Security check each month, unless you are not yet receiving Social Security benefits. If you are not receiving benefits, Medicare will bill you directly. The standard Part B premium changes each year; you can find the current amount on Medicare.gov or by calling 1-800-MEDICARE (1-800-633-4227).

Late enrollment penalties and how to avoid them

If you miss your Initial Enrollment Period and do not have a may have access to reason, you will owe a late enrollment penalty for as long as you have Part B. The penalty is 10 percent of the standard Part B premium for each full 12-month period you were not enrolled when you could have been. If the standard premium is $165 per month and you were late by two years, your penalty would be 20 percent of $165, or about $33 per month, added to your regular premium permanently.

The only way to avoid this penalty is to enroll during your Initial Enrollment Period or to have a may have access to reason for a Special Enrollment Period. If you believe you have a may have access to reason — such as employer coverage that ended, a move out of your plan's service area, or loss of Medicaid — contact Social Security or Medicare to discuss it. You will need to provide proof of the may have access to event.

If you already owe a late enrollment penalty and want to reduce it, you can drop Part B and re-enroll during a future General Enrollment Period. However, this does not erase the penalty you already owe; it only prevents the penalty from growing larger. Most people should not drop Part B once they have it.

Special situations: employer coverage and other exceptions

If you are still working and covered by your employer's health plan when you turn 65, you do not have to enroll in Part B right away. You have a Special Enrollment Period of eight months after your employment ends or your coverage stops — whichever comes first — to enroll without penalty. This is one of the few ways to delay enrollment without owing a penalty.

To use this exception, you must have been covered by an employer plan (either your own or your spouse's) when you turned 65, and that coverage must have ended. When you enroll during your Special Enrollment Period, bring proof of the coverage and the date it ended. Social Security or Medicare can tell you what documents they need.

If you are a federal employee, railroad retiree, or covered under TRICARE (military health coverage), you may have different enrollment rules. Contact your benefits administrator or call 1-800-MEDICARE to confirm your situation before your 65th birthday.

Common mistakes to avoid

The biggest mistake is waiting too long to enroll. Many people assume Medicare enrollment is automatic or that they can enroll anytime without penalty. It is not automatic, and delays are expensive. Mark your Initial Enrollment Period on your calendar as soon as you know when you will turn 65.

Another common mistake is not reporting a may have access to event. If your employer coverage ends, your Medicaid is dropped, or you move out of your plan's service area, tell Social Security or Medicare right away. These events open a Special Enrollment Period, but only if you report them within the required timeframe — usually within 60 days of the event.

Do not assume you are automatically enrolled in Part B just because you enrolled in Part A. Part A (hospital insurance) and Part B (medical insurance) are separate. You must enroll in each one. If you are receiving Social Security benefits, you are usually enrolled in Part A automatically at 65, but you still have to enroll in Part B.

Frequently Asked Questions

Can I enroll in Part B before I turn 65?

Yes, you can enroll up to three months before your 65th birthday. This is part of your Initial Enrollment Period. Enrolling early does not start your coverage early — it will begin the first day of the month you turn 65 — but it ensures you do not miss the important date.

What if I miss the important date but have a good reason?

If you have a may have access to event — such as employer coverage ending, loss of Medicaid, or a move out of your plan's service area — you may have a Special Enrollment Period. Contact Social Security or Medicare to explain your situation and provide proof of the event. You will need to act within the required timeframe, usually 60 days after the event.

Do I have to enroll in Part B if I have employer coverage?

No. If you are covered by an active employer plan, you can delay Part B enrollment. You have eight months after your coverage ends to enroll without penalty. However, once your employer coverage stops, you should enroll promptly to avoid a gap in coverage.

How much does Part B cost?

The standard Part B premium changes each year. For 2024, the standard premium is $175.10 per month, but higher-income beneficiaries pay more. The exact amount depends on your income from two years prior. You can find the current premium on Medicare.gov or by calling 1-800-MEDICARE.

What if I enroll late — can the penalty be removed?

No, the late enrollment penalty cannot be removed once it is applied. It stays with you for life. The only way to stop it from growing is to avoid dropping and re-enrolling in Part B. If you believe you had a may have access to reason that was not recognized, you can request a review, but this is difficult and rarely successful.