Medicare enrollment opens at 65, but the exact timing matters for your costs

You can enroll in Medicare starting three months before the month you turn 65. If your birthday is June 15, enrollment opens March 1. The standard enrollment period lasts seven months — three months before, the month of your birthday, and three months after. Missing this window can lock you into higher premiums for life, so the timing is not flexible once you pass 65.

If you are already receiving Social Security when you turn 65, Medicare enrollment happens automatically. You will receive your Medicare card in the mail about two weeks before your 65th birthday. If you are not yet taking Social Security, you must enroll yourself through Medicare.gov, by phone, or in person at a Social Security office.

The rules change if you are still working and covered by your employer's health plan. You may be able to delay enrollment without penalty, but only if your employer plan covers 20 or more employees. Delaying when you do not meet this exception means paying a permanent surcharge on your Part B and Part D premiums.

Key Takeaways

  • Your initial enrollment period is seven months long — three months before your 65th birthday, the month you turn 65, and three months after.
  • If you miss this window, you pay a 10 percent surcharge on Part B premiums for each full year you delayed, and a 1 percent surcharge on Part D premiums for each month you delayed.
  • You do not need to enroll if you are already receiving Social Security — Medicare enrolls you automatically.
  • If your employer covers 20 or more employees and you are still working, you may delay Part B without penalty, but you must still enroll in Part A.
  • Special enrollment periods open if you lose employer coverage, retire, or move to a new state, and these periods have their own important date.

What happens if you enroll during your initial seven-month window

Enrolling on time means your coverage starts the first day of the month you turn 65, or the first day of the month after you enroll, whichever is later. If you enroll in February for a June birthday, coverage begins June 1. If you enroll in July after a June birthday, coverage begins August 1.

Part A (hospital insurance) is free for most people at 65 if you or your spouse paid Medicare taxes for at least 10 years. Part B (medical insurance) costs a monthly premium, which changes each year. In 2024, the standard Part B premium is $164.90 per month, but higher earners pay more. Part D (prescription drug coverage) is optional and costs vary by plan.

During your initial enrollment period, you can choose Original Medicare (Part A and Part B) plus a separate Medigap or Part D plan, or you can choose a Medicare Advantage plan (Part C), which bundles hospital, medical, and usually prescription drug coverage. This choice affects your costs and which doctors you can see, so comparing plans before your enrollment important date is important.

Penalties for missing your initial enrollment period

If you do not enroll in Part B during your initial seven-month window and you do not have a may have access to reason to delay, you pay a permanent 10 percent surcharge on your Part B premium for each full year you were may be able to access but not enrolled. If you were may be able to access for eight years before enrolling, you pay a 80 percent surcharge on top of the standard premium for the rest of your life.

Part D (prescription drug) carries a 1 percent surcharge per month of delay. If you go 24 months without coverage, the surcharge is 24 percent of the national base premium, and again, this penalty stays with you permanently. These surcharges do not go away if you switch plans or move to a different state.

The only way to avoid these penalties is to have a may have access to reason for the delay. The most common reason is employer coverage through a current job. If you were covered by an employer plan with 20 or more employees, you have a special enrollment period of eight months after you lose that coverage or retire, whichever comes first. You must enroll during this window to avoid penalties.

Employer coverage and delayed enrollment

If you are still working at 65 and your employer offers health insurance, you may delay Part B without penalty. This only works if your employer has 20 or more employees. You must still enroll in Part A at 65 — Part A has no surcharge for delay, but waiting can affect your coverage start date.

When you retire or lose your employer coverage, you have eight months to enroll in Part B without penalty. This period is called a special enrollment period. If you miss this eight-month window, the standard surcharge rules explore. You do not get a second chance.

Your employer may require you to enroll in Medicare before they will cover you under their retiree plan, or they may coordinate benefits in a way that makes your employer plan secondary. Check with your employer's benefits office before you turn 65 to understand how their plan works with Medicare.

Special enrollment periods outside your initial window

If you miss your initial seven-month enrollment period, you may still have a special enrollment period if you experienced a may have access to life event. These events include losing employer coverage, retiring, moving to a new state, losing Medicaid, or having a change in your immigration status. Each event has its own enrollment window, usually 60 days or eight months depending on the reason.

You must report the may have access to event to Medicare and provide proof — a letter from your employer, a notice from your health plan, or documentation of your move. Without proof, Medicare may deny your request for a special enrollment period and explore the standard surcharge rules.

If you are already enrolled in Medicare and you experience a may have access to event during the year, you may also change your Medicare Advantage or Part D plan outside the normal open enrollment period. This is different from a special enrollment period for initial enrollment, but the concept is similar — the event opens a limited window to make changes.

How to enroll when your important date approaches

You can enroll online at Medicare.gov, by phone at 1-800-MEDICARE, or in person at your local Social Security office. Online enrollment is the fastest — you can complete it in 10 to 15 minutes if you have your Social Security number and information about any current health coverage.

By phone, a representative will walk you through the same questions and can answer questions about plan options. Wait times are usually shorter early in the week and early in the day. In person, a Social Security representative can help you enroll and answer questions, though you may need to schedule an appointment.

If you are enrolling close to your important date, do not wait until the last day. Processing can take up to two weeks, and if your enrollment is not processed before your important date passes, you may miss your window. Enroll at least one week before your important date to be safe.

Medicare open enrollment and annual changes

After your initial enrollment, you can change your Medicare plan once a year during the annual open enrollment period, which runs October 15 to December 7. Changes made during this period take effect January 1 of the following year. This is when you can switch from Original Medicare to Medicare Advantage, change your Medigap plan, or switch your Part D prescription drug plan.

Outside of open enrollment, you can only change plans if you experience a may have access to life event — moving, losing coverage, getting married or divorced, or a significant change in your health or income. These changes usually take effect the first day of the following month.

Even if you do not plan to change plans, reviewing your coverage each year during open enrollment is worth your time. Plan premiums, deductibles, and covered drugs change every year, and a plan that made sense last year may not be the best choice this year.

Frequently Asked Questions

Can I enroll in Medicare before I turn 65?

Yes. You can enroll starting three months before the month you turn 65. For example, if you turn 65 in September, you can enroll starting June 1. Your coverage will not start until the month you turn 65 or the month after you enroll, whichever is later.

What if I am still working and do not want Medicare yet?

If your employer has 20 or more employees, you can delay Part B without penalty. You must still enroll in Part A at 65. When you retire or lose your employer coverage, you have eight months to enroll in Part B without penalty. After that, surcharges explore.

Do I have to choose a plan during my initial enrollment period?

Yes. If you do not actively choose a plan, Medicare will not automatically enroll you in Part B or Part D. Part A enrollment is automatic if you are receiving Social Security, but you must choose Part B and Part D yourself or face penalties.

What happens if I enroll late but have a good reason?

If you have a may have access to reason for the delay — such as employer coverage, a move, or loss of Medicaid — you may have a special enrollment period that lets you enroll without penalty. You must provide proof of the may have access to event to Medicare within the required timeframe.

Can I change my mind after I enroll?

You have a limited time to change your mind after you enroll. If you enroll during your initial period, you can change your plan choice once during that seven-month window. After that, you can only change plans during the annual open enrollment period or if you experience a may have access to life event.