You don't have to sign up for Medicare at 65, but waiting usually costs you money for the rest of your life

Medicare enrollment is not automatic at 65. You have to sign up yourself, either through Social Security, Medicare.gov, or by phone. If you delay past your 65th birthday without a valid reason, you will pay a permanent penalty on your Part B and Part D premiums — meaning higher monthly bills every month you have Medicare, even decades later.

The main exception is if you are still working and covered by your employer's health plan. If your employer has 20 or more employees, you can delay Part B without penalty. But you still need to sign up for Part A (hospital insurance) at 65, and the rules around Part D (prescription drug coverage) are stricter — you can only delay that without penalty if your employer plan covers drugs as well as Medicare would.

Key Takeaways

  • You must sign up for Medicare Part A and Part B during your initial enrollment period, which starts three months before the month you turn 65 and ends three months after.
  • If you miss this window and do not have employer coverage, you will pay a 10 percent penalty on Part B premiums for as long as you have Medicare.
  • Part D (prescription drug) penalties are 1 percent per month of delay, and they also last for life.
  • If you are still working and covered by an employer plan with 20 or more employees, you can delay Part B without penalty, but you should still sign up for Part A.
  • You can sign up through Social Security, Medicare.gov, by phone at 1-800-MEDICARE, or at your local Social Security office.

Your initial enrollment period and what happens if you miss it

Your initial enrollment period is seven months long: it starts three months before the month you turn 65 and ends three months after. If you turn 65 in June, your window opens in March and closes in September. During this time, you can sign up for Medicare with no penalty, no matter what your health situation is.

If you sign up during this window, your coverage usually starts on the first day of the month you turn 65. If you sign up after your birthday month, coverage starts the first day of the following month.

If you miss this entire seven-month window and you do not have employer coverage, you will owe a penalty. For Part B, it is 10 percent of the standard premium for each 12-month period you could have had it but did not. That penalty is permanent — it stays on your bill for life. The same applies to Part D: 1 percent per month of delay, also permanent.

When you can delay without penalty: employer coverage rules

If you are still working at 65 and your employer offers health insurance, you may be able to delay Part B without penalty. The rule depends on your employer's size. If your employer has 20 or more employees, you can delay Part B as long as you stay covered by that plan. Once you leave the job or lose the coverage, you have eight months to sign up for Part B without penalty.

Part A is different. You should still sign up for Part A at 65 even if you have employer coverage, because Part A is hospital insurance and does not conflict with employer plans. Delaying Part A can also trigger a penalty, though it is smaller than Part B's.

Part D (prescription drug coverage) has its own rule. You can only delay Part D without penalty if your employer plan covers prescription drugs at least as well as Medicare Part D does. If it does not, you should sign up for Part D during your initial enrollment period. If you delay and your employer plan later ends, you will owe the 1 percent monthly penalty on Part D for the months you were uninsured.

How to sign up and where to do it

You have three main ways to sign up for Medicare. The easiest for most people is online at Medicare.gov. You can create an account, review your options, and submit your enrollment in about 15 minutes. You will need your Social Security number and information about any current health coverage.

You can also sign up through Social Security. If you are already receiving Social Security benefits, you are usually signed up for Medicare automatically at 65 — but check your Social Security account online or call 1-800-772-1213 to confirm. If you are not yet receiving benefits, you can sign up for both Social Security and Medicare at the same time through Social Security's website or office.

A third option is to call 1-800-MEDICARE (1-800-633-4227). A representative can walk you through your options and enroll you over the phone. The line is open 24 hours a day, seven days a week. You can also visit your local Social Security office in person, though this usually takes longer than calling or going online.

What happens after you sign up

After you enroll, Medicare will mail you a Medicare card within two to three weeks. Your coverage usually starts on the first day of the month you turn 65 or the first day of the month after you sign up, depending on when you submitted your enrollment.

You will also receive information about your coverage options. If you are in Original Medicare (Part A and Part B), you can choose to add a Medigap plan or a Medicare Advantage plan. These choices have their own enrollment important date, usually 60 days after your Part B coverage starts. Missing these important date can also trigger penalties or lock you out of certain plans until the next open enrollment period.

Common mistakes to avoid

The biggest mistake is assuming you are automatically signed up. You are not — unless you are already receiving Social Security benefits, in which case you usually are. Check your account or call Social Security to be sure.

Another common error is delaying Part D thinking you do not need it yet. If you do not take any prescription drugs now, you might think you can sign up later. But the 1 percent monthly penalty for Part D applies from the month you first became may be able to access, not from the month you actually need it. If you delay three years, you owe 36 percent extra on your Part D premium for life.

A third mistake is not understanding your employer coverage rules. If you work for a small employer (fewer than 20 employees), you cannot delay Part B without penalty. If you are unsure of your employer's size or whether your plan qualifies, call Medicare at 1-800-MEDICARE and ask — it is better to sign up and cancel later if needed than to miss the important date.

Frequently Asked Questions

What if I turn 65 but I am not ready to retire yet?

You still need to sign up for Medicare at 65 unless you have employer coverage through a company with 20 or more employees. You can have both Medicare and employer coverage at the same time. Medicare becomes your primary insurance once you turn 65, even if you are still working.

Can I sign up for Medicare after I turn 65 without a penalty?

Only if you have a valid reason. The main reason is employer coverage. If you worked for a company with 20 or more employees and had their health plan, you have eight months after you leave that job or lose the coverage to sign up for Part B without penalty. Otherwise, you must sign up during your seven-month initial enrollment period.

What if I already missed my enrollment important date?

You can still sign up, but you will owe a penalty. The penalty is permanent and applies to every month you have Medicare. You can sign up during the General Enrollment Period, which runs January 1 to March 31 each year, with coverage starting July 1. Call 1-800-MEDICARE or visit Medicare.gov to enroll.

Do I have to choose a Medicare plan at 65, or can I do it later?

You must choose during your initial enrollment period or you may face penalties or limited plan options. If you do not choose, you will be placed in Original Medicare (Part A and Part B) by default. You can add a Medigap or Medicare Advantage plan within 60 days of your Part B start date without penalty.

What if I am not a U.S. citizen?

You must be a U.S. citizen or a lawful permanent resident who has lived in the United States for at least five years to sign up for Medicare. If you do not meet these requirements, you cannot enroll. Contact Medicare at 1-800-MEDICARE if you have questions about your immigration status and Medicare may be able to access.