You must sign up for Medicare during specific windows, or you pay a penalty for as long as you have coverage

Medicare enrollment is not automatic. You become may be able to access at 65, but you have to take action during one of three enrollment periods, or you face a permanent monthly penalty added to your premium. The penalty is 10 percent of the standard Part B premium for each year you delayed — so waiting five years costs you an extra 50 percent on your premium forever, even after you finally sign up.

The three enrollment windows are: your Initial Enrollment Period (the seven months centered on your 65th birthday), the General Enrollment Period (January 1 to March 31 each year), and Special Enrollment Periods (triggered by specific life events like losing employer coverage). Missing all three in a given year means waiting until the next General Enrollment Period and paying the penalty retroactively.

If you are still working at 65 and covered by your employer's health plan, you may be able to delay without penalty — but only if you meet strict conditions. If you are on Social Security already, you are usually signed up automatically. The rules differ slightly for Part A, Part B, Part D, and Medigap, so timing matters differently for each.

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 — and this is the only window where you avoid penalties if you sign up late.
  • If you miss your Initial Enrollment Period, you can sign up during the General Enrollment Period (January 1 to March 31), but you will owe a permanent penalty on Part B and Part D premiums.
  • If you are still working at 65 and covered by your employer's health plan, you may delay Part B without penalty, but you must sign up within eight months of losing that coverage to avoid the penalty.
  • If you are already receiving Social Security benefits before 65, you are usually signed up for Medicare automatically three months before your 65th birthday.
  • Special Enrollment Periods let you sign up outside the normal windows without penalty if you lose employer coverage, move out of your plan's service area, or experience other may have access to events.

Your Initial Enrollment Period: The seven-month window centered on your 65th birthday

Your Initial Enrollment Period is your main chance to sign up without penalty. It spans seven months: three months before the month you turn 65, the month you turn 65 itself, and three months after. For example, if you turn 65 in June, your period runs from March through September.

During this window, you can sign up for Part A (hospital insurance), Part B (medical insurance), Part D (prescription drug coverage), and Medigap (supplemental coverage) without any delay penalty. Even if you sign up in the last month of your period — three months after your birthday — you are still protected from the 10 percent permanent surcharge on Part B and the 1 percent per month surcharge on Part D.

Coverage start dates depend on when you sign up. If you sign up in the month you turn 65 or earlier, Part A and Part B coverage usually begins on the first day of the month you turn 65. If you sign up after that month, coverage is delayed by one or two months. Signing up in September when your birthday was in June means your Part B coverage starts in November.

General Enrollment Period: January through March, with a three-month delay

If you miss your Initial Enrollment Period, the General Enrollment Period runs every year from January 1 through March 31. You can sign up during this window, but coverage does not start until July 1 of that year — a three-month wait. You also owe the permanent penalty on Part B and Part D.

The Part B penalty is 10 percent of the standard premium for each full year you were may be able to access but not signed up. If you were may be able to access at 65 and did not sign up until age 68, you owe 30 percent extra on your Part B premium for life. The Part D penalty is 1 percent of the national average premium for each month you were without creditable drug coverage, rounded to the nearest dollar and added to your premium each year.

The General Enrollment Period is a safety net, but it is expensive. If you realize you missed your Initial Enrollment Period, check whether a Special Enrollment Period applies to you first — it may let you avoid the penalty.

Still working at 65: Delaying Part B without penalty if you have employer coverage

If you are still employed and covered by your employer's health plan at 65, you may be able to delay Part B without triggering the penalty. This is called the Special Enrollment Period for employer coverage. You must meet two conditions: your employer must have at least 20 employees, and you must be actively working (not retired but still on the payroll).

Under these conditions, you can skip your Initial Enrollment Period and sign up later without the 10 percent Part B penalty. However, you must sign up within eight months of losing your employer coverage — either by retiring, being laid off, or having your coverage end. If you wait longer than eight months, the penalty applies retroactively from the month your employer coverage ended.

Part A (hospital insurance) works differently. You can usually delay Part A without penalty as long as you have employer coverage, even after 65. But once you lose that coverage, you have only two months to sign up for Part A before a penalty kicks in. Part D (prescription drug) also has its own penalty rules — if you go without creditable drug coverage, the 1 percent monthly penalty applies even if you had employer coverage.

Already receiving Social Security: You are usually signed up automatically

If you are already receiving Social Security retirement or disability benefits when you turn 65, Medicare usually signs you up automatically. About three months before your 65th birthday, you will receive a notice in the mail explaining your coverage and your options. You do not have to do anything — Part A and Part B coverage begins on the first day of the month you turn 65.

This automatic enrollment applies to most people on Social Security. However, you still need to make choices about Part D (prescription drug coverage) and Medigap (supplemental coverage) if you want them. You have the same seven-month Initial Enrollment Period to choose a Part D plan or Medigap policy. If you do not choose a Part D plan during this window, you owe the 1 percent monthly penalty when you eventually sign up.

If you are not receiving Social Security yet but will be soon, contact Social Security about three months before your 65th birthday to confirm you are on track for automatic enrollment. If you are not receiving Social Security and do not plan to, you must sign up for Medicare yourself during your Initial Enrollment Period.

Special Enrollment Periods: Signing up outside the normal windows

A Special Enrollment Period lets you sign up for Medicare without penalty outside the normal enrollment windows if you experience a may have access to event. The most common trigger is losing employer health coverage — through retirement, job loss, or your employer dropping the plan. Other triggers include moving out of your plan's service area, losing Medicaid coverage, or being wrongly denied enrollment.

The length of your Special Enrollment Period depends on the event. If you lose employer coverage, you usually have eight months to sign up for Part B without penalty. If you move out of your plan's service area, you have two months. If you lose Medicaid, you have two months. You must sign up within these windows — after that, the penalty applies.

To use a Special Enrollment Period, you need to prove the may have access to event. Have your employer's coverage termination letter, your move documentation, or your Medicaid termination notice ready when you contact Medicare. You can sign up by phone (1-800-MEDICARE), online at Medicare.gov, or in person at your local Social Security office.

Part D and Medigap: Separate enrollment periods with their own penalties

Part D (prescription drug coverage) and Medigap (supplemental insurance) have their own enrollment rules. For Part D, your Initial Enrollment Period is the same seven-month window as Part A and Part B. If you miss it and do not have creditable drug coverage from another source, you owe a 1 percent monthly penalty on your Part D premium when you eventually sign up — and this penalty is permanent.

Medigap has a different rule in most states. You have a six-month open enrollment period starting the month you turn 65 and are signed up for Part B. During this window, insurance companies cannot deny you or charge you more based on pre-existing conditions. After six months, they can. Some states have different rules, so check your state's insurance commissioner's office if you are in a state with its own Medigap rules.

If you are on Medicare already and want to switch Medigap plans, you have limited options outside the initial six-month window. Some life events — like turning 65, moving, or losing employer coverage — may open a new enrollment period in your state. Contact your state insurance commissioner's office to confirm.

What happens if you miss all the important date

If you miss your Initial Enrollment Period and do not may have access to for a Special Enrollment Period, you must wait for the next General Enrollment Period (January 1 to March 31). Your coverage will not start until July 1, and you will owe the permanent penalty on Part B and Part D.

The penalty is not a one-time fee — it is added to your premium every month for as long as you have Medicare. A five-year delay costs you an extra 50 percent on Part B forever. On Part D, a five-year delay costs you an extra 60 percent (1 percent per month times 60 months) on your prescription drug premium. These penalties do not go away if you switch plans or move to a different state.

The only way to avoid the penalty after missing your Initial Enrollment Period is to prove you may have access to for a Special Enrollment Period. If you lost employer coverage, moved, or experienced another may have access to event, contact Medicare when ready with documentation. If you cannot prove a may have access to event, you are locked into the General Enrollment Period and the penalty.

Frequently Asked Questions

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

You can delay Part B if your employer has at least 20 employees and you are actively working. You have eight months after losing your employer coverage to sign up without penalty. However, you should still sign up for Part A (hospital insurance) during your Initial Enrollment Period, as it has no premium and covers hospital stays.

Can I change my mind after I sign up during my Initial Enrollment Period?

Yes. You have until the end of the calendar year to change your Part B, Part D, or Medigap choices if you signed up during your Initial Enrollment Period. After that, you are locked in until the next annual enrollment period (October 15 to December 7) unless you may have access to for a Special Enrollment Period.

Do I have to sign up for Part B if I do not want it?

You are not required to sign up for Part B, but if you delay and later change your mind, you will owe the 10 percent permanent penalty unless you may have access to for a Special Enrollment Period. If you are still working with employer coverage, you can delay without penalty as long as you sign up within eight months of losing that coverage.

What if I am not a U.S. citizen but live here legally?

You must be a U.S. citizen or permanent resident for at least five years to sign up for Medicare. If you do not meet this requirement at 65, contact Medicare to learn when you become may be able to access. Timing rules are the same once you do become may be able to access.

Can I sign up for Medicare before I turn 65?

No. Your Initial Enrollment Period cannot start until three months before the month you turn 65. If you try to sign up earlier, your process will be rejected. The earliest you can sign up is three months before your 65th birthday month.