You must register during specific windows, or you pay a penalty for life

Medicare enrollment is not open year-round. You have a seven-month Initial Enrollment Period centered on your 65th birthday — three months before, the month you turn 65, and three months after. If you miss this window, you enter a General Enrollment Period each January through March, but you will owe a permanent 10 percent monthly penalty on Part B premiums and a 1 percent monthly penalty on Part D (prescription drug) premiums for every 12 months you delayed. These penalties stay on your bill for life.

The exact important date depends on when you were born and which parts of Medicare you need. Some people — those still working with employer coverage, or those on certain disability programs — have different rules that let them delay without penalty. But if you turn 65 and do nothing, you will be uninsured and liable for the penalty.

Key Takeaways

  • Your Initial Enrollment Period runs for seven months: three months before your 65th birthday, the month you turn 65, and three months after.
  • If you miss the Initial Enrollment Period, you can register during General Enrollment (January through March each year), but you will owe a permanent 10 percent monthly penalty on Part B and 1 percent on Part D for every year you waited.
  • If you are still working at 65 with employer health insurance, you may be able to delay Part B without penalty, but you must notify Social Security in writing.
  • The important date to register for Part D (prescription drugs) is the same as Part B; missing it costs you 1 percent per month for life, even if you do not take many prescriptions.
  • You register through Social Security (in person, by phone, or online), Medicare.gov, or your local Social Security office — not through your doctor or insurance company.

The seven-month Initial Enrollment Period around your 65th birthday

Your Initial Enrollment Period begins three months before the month you turn 65 and ends three months after. For example, if you turn 65 in June, your window opens in March and closes in September. You can register at any point during those seven months, and coverage will begin on the first day of the month you turn 65 (if you register by the 15th of that month) or the first day of the following month (if you register after the 15th).

This is the only time you can register for Part A (hospital insurance) and Part B (medical insurance) without a waiting period or penalty. Part A is usually free if you or your spouse paid Medicare taxes for at least 10 years. Part B has a monthly premium that changes each year. You must decide whether to take both, Part A only, or neither during this window.

If you are still working at 65 with health insurance through your employer, you can delay Part B without penalty — but only if your employer has 20 or more employees. You must tell Social Security in writing that you are relying on employer coverage. When you finally register for Part B (after you retire or lose the coverage), you will not owe a penalty. This exception does not explore to Part A; you should still register for Part A even if you delay Part B.

What happens if you miss the Initial Enrollment Period

If you do not register during your seven-month window, you move into the General Enrollment Period, which runs January 1 through March 31 each year. You can register then, and coverage begins July 1 of that year. However, you will owe a permanent penalty on Part B: 10 percent of the standard monthly premium for every 12 months you delayed. If you waited two years, your Part B premium will be 20 percent higher than the standard rate, and that surcharge stays on your bill for the rest of your life.

The same rule applies to Part D (prescription drug coverage). If you go without Part D coverage for 63 days or more in a row, you owe a 1 percent monthly penalty on the lowest-cost plan available in your area for every month you were uninsured. This penalty also lasts for life. Even if you rarely take prescriptions, registering for Part D during your Initial Enrollment Period costs nothing if you do not use it, but skipping it can cost you permanently.

There is no way to remove these penalties once they are applied. You cannot appeal them or ask for an exception based on hardship or confusion. The only exception is if you were receiving certain disability benefits (SSI or SSDI) and did not know you had to register — in that case, you may be able to get the penalty waived, but you must contact Social Security to request it.

Special enrollment periods for people with employer coverage or life changes

If you lose employer health insurance — because you retire, are laid off, or your employer stops offering coverage — you have a two-month Special Enrollment Period to register for Medicare without penalty. This period begins the month you lose the coverage. You must show proof that you had employer insurance and the date it ended.

If you are on COBRA (the federal program that lets you keep employer insurance after leaving a job), your Special Enrollment Period starts when COBRA ends, not when you first lose the employer plan. Similarly, if you are on Medicaid or CHIP (state programs for low-income people), losing that coverage opens a Special Enrollment Period.

If you move to a new state, get married, or have another major life change, you may also have a Special Enrollment Period for Part D only. These windows are narrower and shorter than the Initial Enrollment Period, so contact Medicare.gov or call 1-800-MEDICARE to confirm your dates.

How to register: the three routes

Social Security: You can register in person at your local Social Security office, by phone at 1-800-772-1213 (TTY 1-800-325-0778), or online at ssa.gov. You will need your Social Security number, proof of citizenship or legal residency, and proof of age (a birth certificate or passport). If you are registering for Part B or Part D, you will also need information about any current health or prescription drug coverage. Registration by phone or online is usually faster than in person.

Medicare.gov: You can create an account on Medicare.gov and register for Part A and Part B online. This route does not require you to visit a Social Security office. You will need the same documents as above. Registration on Medicare.gov typically takes 10 to 15 minutes.

Your local Social Security office: If you prefer to register in person, bring your Social Security card, proof of age, and proof of citizenship or legal residency. Bring any documents related to employer coverage if you are claiming an exception to the penalty rules. Offices are usually open Monday through Friday, 9 a.m. to 4 p.m., but hours vary by location. Call ahead to confirm.

Do not register through your doctor, hospital, or insurance company. They cannot process Medicare enrollment, and registering with them will not count toward your important date. Only Social Security and Medicare.gov have the authority to enroll you.

Timeline for coverage to begin after you register

Coverage start dates depend on when you register within your enrollment period. If you register by the 15th of the month you turn 65, your Part A and Part B coverage begins on the first day of that month. If you register after the 15th, coverage begins on the first day of the next month. For Part D, coverage begins on the first day of the month after you register, regardless of the date you register within that month.

If you register during General Enrollment (January through March), coverage does not begin until July 1 of that year. This means if you register in January, you will have no Medicare coverage from January through June — a gap that can be expensive if you need medical care.

You will receive a Medicare card in the mail within two to four weeks of registration. Until it arrives, you can use a temporary proof of enrollment from Social Security or Medicare.gov. Bring this proof to your doctor or hospital if you need care before the card arrives.

Common mistakes that trigger penalties

The most common mistake is assuming you have time after 65. Many people turn 65, do nothing, and assume they can register later without consequence. By the time they realize the important date has passed, they have already entered the General Enrollment Period and owe a penalty. Set a calendar reminder three months before your 65th birthday.

Another mistake is registering for Part A only and skipping Part B. If you are not working and do not have employer coverage, you should register for both. Part A covers hospital stays; Part B covers doctor visits and outpatient care. Skipping Part B and registering later will cost you a permanent 10 percent penalty on the premium.

A third mistake is not telling Social Security that you are still working with employer coverage. If you are 65, still employed, and have health insurance through your job, you must notify Social Security in writing that you are relying on that coverage. If you do not, and you do not register for Part B, you will owe a penalty when you finally do register. The written notice protects you; a phone call or email does not count.

Frequently Asked Questions

Can I register for Medicare before I turn 65?

Yes. Your Initial Enrollment Period begins three months before the month you turn 65. You can register as early as that date. Registering early does not affect your coverage start date — it will still begin on the first day of the month you turn 65 (or the next month, depending on when you register). There is no advantage to registering early, but there is no disadvantage either.

What if I was born on the first day of the month?

Medicare counts you as turning 65 on the first day of the month before your actual birth date. So if you were born on June 1, Medicare treats you as turning 65 on May 1. Your Initial Enrollment Period runs from February through August. Check your Social Security statement or call 1-800-772-1213 to confirm your official Medicare birthday.

Do I have to register for Part D if I do not take any prescriptions?

You do not have to, but you should. If you skip Part D and do not take prescriptions for 63 days or more, you will owe a 1 percent monthly penalty for life when you finally register. The penalty is based on the lowest-cost plan in your area, which is usually $5 to $15 per month. Registering for Part D during your Initial Enrollment Period costs nothing if you do not use it, so the penalty is avoidable.

What if I was not a U.S. citizen until after I turned 65?

You have a seven-month Initial Enrollment Period starting the month you become a U.S. citizen. You will need to show proof of citizenship (a naturalization certificate or passport) when you register. You will not owe a penalty for the time before you became a citizen, because you were not yet may be able to access.

Can I register for Medicare if I am still working past 65?

Yes. You can work as long as you want and still register for Medicare at 65. If your employer has 20 or more employees and offers health insurance, you can delay Part B without penalty by notifying Social Security in writing. You should still register for Part A. If your employer has fewer than 20 employees, you should register for both Part A and Part B at 65 to avoid penalties.