Enroll during your Initial Enrollment Period, which starts three months before the month you turn 65

Your Initial Enrollment Period is a seven-month window that begins three months before your 65th birthday month and ends three months after it. If you turn 65 in June, your period runs from March through September. During this window, you can enroll in Medicare Part A (hospital insurance) and Part B (medical insurance) without penalties.

You do not have to wait until you turn 65 to start the process. In fact, you should begin about three months before your birthday. This gives you time to gather documents, understand your options, and complete enrollment before coverage begins. Most people's Part A and Part B coverage starts on the first day of the month they turn 65.

If you miss your Initial Enrollment Period, you can still enroll during the General Enrollment Period, which runs January 1 through March 31 each year. However, late enrollment penalties explore — your Part B premium increases by 10 percent for each full year you delayed, and that increase stays with you permanently. Part A carries a similar penalty of 10 percent if you delayed without may have access to for an exception.

Key Takeaways

  • Your Initial Enrollment Period is seven months long: three months before, the month of, and three months after you turn 65.
  • You should start the enrollment process about three months before your birthday to avoid rushed decisions or missed important date.
  • If you miss your Initial Enrollment Period, you face permanent premium increases unless you may have access to for a Special Enrollment Period.
  • If you are still working and have employer health insurance, you may have a Special Enrollment Period that extends your important date.
  • Part D (prescription drug coverage) has its own enrollment important date separate from Part A and B, and missing it also triggers a permanent penalty.

Special Enrollment Periods: When you can enroll outside the standard window

A Special Enrollment Period gives you extra time to enroll if you meet certain conditions. The most common reason is employer coverage: if you or your spouse are still working and covered by an employer or union health plan, you can enroll in Medicare without penalty even after your Initial Enrollment Period ends. This protection lasts as long as you have that coverage, plus eight months after it ends.

Other situations that trigger a Special Enrollment Period include losing health coverage, moving out of your plan's service area, or having your plan terminate. You also may have access to if you are a U.S. citizen or permanent resident who was outside the United States for more than six months in a row. Each situation has its own rules about how long the period lasts, so you will need to confirm your specific circumstances with Medicare.

To use a Special Enrollment Period, you must have documentation of the may have access to event — a letter from your employer showing your coverage dates, a notice from your plan saying it is ending, or proof of your residency status. Without this proof, Medicare will treat your enrollment as late and explore penalties.

Part D enrollment important date are separate from Part A and B

Part D is prescription drug coverage, and it has its own enrollment window. You can enroll in Part D during your Initial Enrollment Period (the same seven-month window as Part A and B), but you can also enroll during the Annual Enrollment Period, which runs October 15 through December 7 each year. Coverage from an October–December enrollment starts January 1.

Missing your Part D important date carries a permanent penalty of about 1 percent of the national average Part D premium for each month you were without coverage. If you go 63 months without Part D or creditable prescription drug coverage, your penalty is roughly 63 percent of the average premium — and it stays on your bill for life. This penalty applies even if you never use prescription drugs.

If you have creditable coverage through an employer, union, or Veterans Affairs, you do not have to enroll in Part D when ready. Creditable coverage means your plan covers drugs at least as well as Medicare does. When that coverage ends, you have 63 days to enroll in Part D without penalty. After 63 days, the permanent penalty clock starts.

What happens if you enroll late

Late enrollment penalties are permanent and compound over time. For Part B, a 10 percent increase on a $165 monthly premium (the 2024 standard) means an extra $16.50 per month forever. If you delay five years, your penalty is 50 percent — an extra $82.50 per month for the rest of your life. The same math applies to Part A if you do not have it through work.

Part D penalties work differently but are equally permanent. The penalty is calculated as a percentage of the national average Part D premium and adjusts each year, but once it attaches to your record, it never goes away. You cannot remove it by enrolling later or by switching plans.

The only way to avoid a late penalty is to have a may have access to reason for the delay. These reasons are narrow: active employer coverage, creditable drug coverage, a Special Enrollment Period, or being a federal employee with coverage through the Federal Employees Health Benefits Program. If none of these explore to you, the penalty stands.

Enroll through Medicare.gov, Social Security, or your local Social Security office

You can enroll in Medicare three ways. The first is online at Medicare.gov, where you can create an account and submit your enrollment during your Initial Enrollment Period or any time you may have access to for a Special Enrollment Period. This is the fastest route and gives you a record of your submission when ready.

The second is by phone through Social Security at 1-800-772-1213 (TTY 1-800-325-0778). A representative can walk you through the process, answer questions about your specific situation, and submit your enrollment on the spot. Wait times are often long, so call early in the day or use the online option if you can.

The third is in person at your local Social Security office. You will need to bring your Social Security card, proof of citizenship or permanent residency (passport or birth certificate), and proof of residence (utility bill or lease). Walk-in hours vary by location, so call ahead or check the office locator on Social Security's website.

Gather these documents before you enroll

Have your Social Security number, birth date, and citizenship or residency status ready. You will also need information about any current health coverage — the name of your plan, your policy number, and your coverage dates. If you have employer coverage, gather the name of your employer or union and confirmation that the coverage is active.

If you are enrolling in Part D, list all the prescription drugs you currently take, including the dose and frequency. This helps you compare plans and choose one that covers your medications at the lowest cost. You can use the Medicare Plan Finder tool on Medicare.gov to see which plans cover your drugs and what your out-of-pocket costs would be.

If you are using a Special Enrollment Period, collect your documentation of the may have access to event before you start. This might be a termination notice from your plan, a letter from your employer confirming your coverage dates, or proof of your residency status. Having this ready prevents delays if Medicare asks for verification.

Understand the difference between Original Medicare and Medicare Advantage

When you enroll in Part A and Part B, you are choosing Original Medicare — the federal program run by Centers for Medicare & Medicaid Services. Original Medicare covers hospital stays, doctor visits, and some preventive care, but it does not include prescription drugs or dental, vision, or hearing coverage. You will need to enroll in Part D separately for drugs, and you can purchase a Medigap (supplemental) plan to cover costs Original Medicare does not.

Alternatively, you can choose a Medicare Advantage plan (Part C), which is a private insurance plan that covers everything Part A and B do, usually with lower out-of-pocket costs and often includes prescription drugs, dental, and vision. However, Medicare Advantage plans have networks, so you may not be able to see all doctors, and coverage outside the network is limited or nonexistent.

You do not choose between Original Medicare and Medicare Advantage at the same time. You enroll in Part A and B first (or you are automatically enrolled if you are receiving Social Security). Then, during the Annual Enrollment Period (October 15 through December 7), you can switch to a Medicare Advantage plan or switch back to Original Medicare. Your choice takes effect January 1.

Frequently Asked Questions

What if I am still working at 65 — do I have to enroll in Medicare?

If you or your spouse have employer coverage, you do not have to enroll in Part B when ready. However, you must enroll in Part A (hospital insurance) if you are receiving Social Security benefits. When your employer coverage ends, you have eight months to enroll in Part B without penalty. After that, late penalties explore.

Can I enroll in Medicare before I turn 65?

You can start the enrollment process three months before your 65th birthday, but coverage does not begin until the first day of the month you turn 65. If you turn 65 on any day other than the first of the month, your coverage still starts on the first day of that month.

What happens if I miss the October 15 to December 7 important date for Part D?

If you miss this important date and do not have creditable coverage, you can still enroll during the next Annual Enrollment Period, but a permanent penalty will be added to your premium. The penalty is roughly 1 percent of the national average Part D premium for each month you were without coverage.

Do I lose my Special Enrollment Period if I do not use it right away?

No. If you may have access to for a Special Enrollment Period due to employer coverage, you can use it anytime while you have that coverage, plus eight months after it ends. However, if you may have access to for a different reason (like moving or losing coverage), the period may be shorter, so check with Medicare about your specific situation.

Can I change my mind after I enroll?

Yes, but only during certain windows. During your Initial Enrollment Period, you can change your choices. During the Annual Enrollment Period (October 15 through December 7), you can switch between Original Medicare and Medicare Advantage or change your Part D plan. Outside these windows, changes are limited unless you have a may have access to life event.