You must sign up for Medicare Part A and Part B when you turn 65, or you will face penalties that last for the rest of your life

If you are already receiving Social Security benefits when you turn 65, Medicare will enroll you automatically in Part A (hospital insurance) and Part B (medical insurance). You do not need to do anything. However, if you are not yet taking Social Security, you must sign up for Medicare yourself during your enrollment window, which begins three months before the month you turn 65 and ends three months after. Missing this window triggers a permanent penalty on your Part B premiums — an extra 10% for each year you delayed — and the same applies to Part D (prescription drug coverage).

The only people who can delay without penalty are those still working and covered by an employer health plan with 20 or more employees. Even then, you must sign up within eight weeks of losing that coverage or retiring, whichever comes first.

Key Takeaways

  • If you receive Social Security, Medicare enrolls you automatically at 65 in both Part A and Part B with no action required on your part.
  • If you do not receive Social Security, you must sign up during your seven-month enrollment window (three months before, the month of, and three months after your 65th birthday) to avoid permanent premium penalties.
  • Part A (hospital insurance) has no premium penalty for late sign-up, but Part B and Part D penalties are 10% per year of delay and never go away.
  • Workers still covered by employer insurance can delay Part B without penalty, but must sign up within eight weeks of losing that coverage.
  • You can sign up online at Medicare.gov, by phone at 1-800-MEDICARE, or in person at your local Social Security office.

What happens if you miss the sign-up window

A late enrollment penalty on Part B stays with you for life. If you were supposed to sign up at 65 and did not, and you enroll at 67, you pay an extra 20% on top of your regular Part B premium forever. The penalty grows by 10% for each full year you delay. Part D (prescription drug) penalties work the same way — 1% of the national average premium per month of delay, and this penalty also never ends.

Part A is different. There is no premium penalty for signing up late, because most people do not pay a premium for Part A if they or their spouse paid Medicare taxes while working. However, if you do owe a Part A premium, signing up late can cost you more per month. The clearer reason to sign up on time is that Part A coverage does not start until the month you enroll, so any hospital stays before that are your responsibility.

When you can delay without penalty

You can postpone Part B without penalty if you are still working and your employer offers health insurance with 20 or more employees. Your employer plan is considered "creditable coverage" — meaning it is as good as or better than Medicare Part B. You do not need to sign up for Part B while you have this coverage.

The moment you retire or lose that employer coverage, your eight-week clock starts. You have eight weeks to sign up for Part B. If you miss that window, the late penalty applies. Part A is different: you can delay Part A without penalty as long as you are working, but you should still sign up when you turn 65 to avoid gaps in coverage if you need hospital care.

If your employer plan ends and you are unsure whether you have eight weeks or a different important date, contact your employer's benefits office or call 1-800-MEDICARE to confirm your specific situation.

How to sign up for Medicare

The easiest way is online at Medicare.gov. Go to the homepage, select "Sign up for Medicare," and follow the steps. You will need your Social Security number, birth date, and citizenship or immigration status. The online process takes about 10 minutes and you receive confirmation when ready.

You can also call 1-800-MEDICARE (1-800-633-4227) and speak to a representative. They can answer questions about your specific situation and enroll you over the phone. The line is open Monday through Friday, 8 a.m. to 8 p.m. Eastern time, and Saturday, 9 a.m. to 1 p.m. Eastern time.

A third option is to visit your local Social Security office in person. Bring your Social Security card, proof of citizenship (passport, birth certificate, or naturalization papers), and proof of residence (utility bill or lease). You can find your local office at ssa.gov or by calling 1-800-772-1213.

What Part A and Part B actually cover

Part A covers inpatient hospital stays, skilled nursing facility care after a hospital stay, hospice, and some home health services. You pay a deductible per hospital stay (the amount changes each year), and then Medicare covers the rest. Most people do not pay a monthly premium for Part A.

Part B covers doctor visits, outpatient care, lab tests, imaging, and preventive services like screenings and vaccines. You pay a monthly premium (the amount depends on your income) and a yearly deductible, then Medicare covers 80% of approved services and you pay 20%. Part B is optional in name only — if you do not sign up on time and you are not still working with employer coverage, you pay a penalty forever.

Deciding whether to take Part B if you are still working

If you are 65 or older and still working with employer coverage, you face a real choice: sign up for Part B now, or wait until you retire. The math depends on your employer plan and your health.

If you sign up for Part B while still working, you pay the Part B premium and your employer plan becomes secondary — it covers what Part B does not. This costs money now but locks in your enrollment date, so you avoid any penalty if you retire later.

If you delay Part B and rely only on your employer plan, you save the Part B premium while working. But when you retire, you have eight weeks to sign up. If you miss that window by even one day, you pay the 10% penalty on Part B for the rest of your life. The penalty is permanent even if you later sign up.

Most people in this situation choose to sign up for Part B at 65 to avoid the risk. But if your employer plan is excellent and you are certain you will remember to sign up within eight weeks of retiring, delaying Part B can save money in the short term.

What to ask your doctor and employer

Before you turn 65, ask your employer's benefits office three questions: Does our health plan meet Medicare's definition of creditable coverage? When does our plan year end? What happens to my coverage when I retire or turn 65? Write down the answers and keep them with your Medicare paperwork.

If you have a chronic condition or see doctors regularly, ask your primary care doctor whether they accept Medicare. Most do, but some do not, and it is better to know before you enroll. If your doctor does not accept Medicare, ask whether they will make an exception for you or whether they can refer you to someone who does.

When to contact Medicare directly

Call 1-800-MEDICARE if you are unsure whether you need to sign up now, if you think you missed the important date, if you are still working and confused about your options, or if you have a medical condition that might affect your coverage choices. You can also call if you signed up but never received your Medicare card in the mail — cards normally arrive within two weeks of enrollment.

If you enrolled and your coverage has not started, or if you see charges on a hospital bill that you think Medicare should have covered, call the number on your Medicare card or contact Medicare directly. Do not wait to resolve billing problems — the sooner you report them, the sooner they can be fixed.

Frequently Asked Questions

What if I turn 65 but I am not a U.S. citizen?

You must be a U.S. citizen or a lawful permanent resident (green card holder) who has lived in the U.S. for at least five years to enroll in Medicare. If you are not yet a permanent resident, you cannot sign up. If you are a permanent resident, bring your green card and proof of five years of residence when you enroll.

Can I sign up for Part A only and skip Part B?

Yes, you can enroll in Part A without Part B if you are still working with employer coverage. However, if you are not working, skipping Part B means paying a penalty later. Most people enroll in both at 65 to avoid complications.

What if I already have private insurance through my job?

If your employer plan has 20 or more employees, you can delay Part B without penalty. When you retire or lose that coverage, you have eight weeks to sign up for Part B. If your employer plan has fewer than 20 employees, you should sign up for Part B at 65 even if you keep your employer plan.

Do I have to sign up for Part D at 65?

Part D (prescription drug coverage) is optional, but if you do not sign up when you turn 65 and you do not have other creditable drug coverage, you pay a penalty when you do enroll. The penalty is 1% of the national average premium per month of delay and never goes away. If you do not take prescription drugs, you can skip Part D without penalty as long as you sign up within 63 days of losing other coverage.

What if I am still working past 65 and do not need Medicare yet?

You still need to make a choice: sign up for Part A and B at 65 (Part A has no premium, so it costs nothing), or delay Part B and risk the penalty later. Most people sign up for Part A at 65 to cover unexpected hospital stays, even if they delay Part B. Call 1-800-MEDICARE to discuss your specific job and coverage before you turn 65.