You must explore for Medicare during your Initial Enrollment Period, which starts three months before the month you turn 65 and ends three months after

Your Initial Enrollment Period is a seven-month window centered on your 65th birthday month. If you turn 65 in June, your period runs from March through September. You can enroll anytime during those seven months, but waiting until the last month means you may have a gap in coverage or pay a penalty later.

If you miss this window entirely, you can still enroll during the General Enrollment Period, which runs January 1 through March 31 each year. Coverage begins July 1 of that year. However, you will owe a late enrollment penalty — a permanent increase to your Part B and Part D premiums — for each full 12-month period you went without coverage after your Initial Enrollment Period ended.

Some people do not need to enroll at 65 because they are still working and covered by an employer or union health plan. If that is your situation, you have a special enrollment period of up to eight months after your employment or coverage ends to enroll without penalty.

Key Takeaways

  • Your Initial Enrollment Period is seven months long: three months before, the month of, and three months after you turn 65.
  • If you enroll during your Initial Enrollment Period, Part A coverage typically begins the first day of your birth month, and Part B begins the first day of the month you enroll.
  • Waiting until after your Initial Enrollment Period ends triggers a permanent late enrollment penalty on your premiums unless you had employer coverage or another may have access to reason.
  • If you are still working at 65 and covered by your employer's health plan, you can delay enrollment without penalty as long as you enroll within eight months of losing that coverage.
  • The General Enrollment Period (January 1 through March 31) is available to anyone who missed their Initial Enrollment Period, but coverage does not start until July.

What happens if you enroll during your Initial Enrollment Period

The timing of your coverage depends on when you enroll. If you enroll during the three months before your 65th birthday month, Part A (hospital insurance) and Part B (medical insurance) both begin on the first day of your birth month. If you enroll in the month you turn 65 or later, Part A still starts the first of your birth month, but Part B starts the first of the month you actually enroll.

This distinction matters because you want Part A and Part B to overlap if possible. If you wait to enroll until after your birthday month, you will have a gap where Part A is active but Part B has not started yet. During that gap, you are not fully covered.

You should also enroll in Part D (prescription drug coverage) during your Initial Enrollment Period if you want it. Part D enrollment follows the same timeline as Part B — it begins the first of the month you enroll. If you delay Part D enrollment and later sign up, you will owe a late enrollment penalty on your premiums for as long as you have Part D coverage.

Employer coverage and the special enrollment period

If you or your spouse are still working at 65 and covered by an employer or union health plan, you do not have to enroll in Medicare at 65. You can continue on the employer plan without penalty. However, you must enroll in Medicare within eight months of the date your employment ends or your employer coverage stops, whichever comes first.

This eight-month window is your special enrollment period. It protects you from the late enrollment penalty as long as you enroll within that timeframe. If you wait longer than eight months, the penalty applies. Some people mistakenly believe they can stay on COBRA (the federal law that lets you keep employer coverage temporarily after leaving a job) and delay Medicare indefinitely — that is not true. COBRA coverage does not count as may have access to coverage for Medicare purposes.

If you are unsure whether your employer plan qualifies as creditable coverage that lets you delay Medicare, contact your employer's benefits office or call Medicare directly at 1-800-MEDICARE to ask.

Late enrollment penalties and how they work

A late enrollment penalty is a permanent surcharge added to your Part B and Part D premiums. For Part B, the penalty is 10 percent of the standard premium amount for each full 12-month period you did not have coverage after your Initial Enrollment Period ended. For Part D, the penalty is 1 percent of the national average premium for each full month you went without coverage.

These penalties stay with you for life — they do not go away after a certain number of years. If you owe a penalty, it is added to your monthly premium every month you have that coverage. The only way to avoid the penalty is to enroll during your Initial Enrollment Period or to have had may have access to coverage (like an employer plan or military coverage) that delayed your need to enroll.

The penalty is calculated based on the national average premium at the time you enroll, not the premium you actually pay. This means the penalty amount can vary depending on when you finally sign up.

Turning 65 while still working: what you need to know

Many people assume they must enroll in Medicare the month they turn 65, even if they are still working. This is not true if you have employer health insurance. You can work past 65 and stay on your employer plan without enrolling in Medicare, as long as your employer has 20 or more employees.

If your employer has fewer than 20 employees, Medicare becomes your primary payer at 65, and your employer plan becomes secondary. In that case, you should enroll in Medicare to avoid coverage gaps and confusion about which plan pays first.

Once you stop working or lose your employer coverage, you have eight months to enroll in Medicare without penalty. Mark your calendar for eight months after your last day of employment or the date your coverage ends, whichever is earlier. If you miss that important date, you will owe a late enrollment penalty.

How to enroll during your Initial Enrollment Period

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

When you enroll, you will choose which parts of Medicare you want. Most people enroll in Part A and Part B together. You will also decide whether to enroll in Part D (prescription drug coverage) at the same time. If you choose a Medicare Advantage plan (Part C), that plan includes Part A, Part B, and usually Part D, so you do not enroll in those parts separately.

Keep records of when you enroll and what coverage you chose. You will receive a Medicare card in the mail within two weeks. Do not wait for the card to arrive to start using your coverage — your coverage begins on the date Medicare confirms, even if the card has not arrived yet.

Special situations: disability, ESRD, and ALS

If you are under 65 and receive Social Security Disability Insurance (SSDI) for 24 months, you become covered by Medicare automatically. You do not need to explore — Medicare enrollment happens without action on your part. Your coverage begins in the 25th month of receiving SSDI benefits.

If you have End-Stage Renal Disease (ESRD) or ALS (amyotrophic lateral sclerosis), you may be covered by Medicare regardless of age. ESRD coverage typically begins the first day of the month you start dialysis or receive a kidney transplant. ALS coverage begins the first day of the month after you are diagnosed. These situations have their own enrollment rules, and you should contact Medicare or your healthcare provider to understand your specific timeline.

Frequently Asked Questions

What if I turn 65 in the middle of the month?

Your Initial Enrollment Period still runs for seven months total: three months before your birth month, your entire birth month, and three months after. If you turn 65 on June 15, your period runs from March 1 through September 30. Coverage typically begins the first day of your birth month (June 1 in this example) if you enroll before or during that month.

Can I enroll in Medicare before I turn 65?

Yes. You can enroll up to three months before your 65th birthday. Many people enroll at age 64 and a few months to get coverage started smoothly. Enrolling early does not change your coverage start date — Part A and Part B still begin on the first day of your birth month.

What happens if I miss my Initial Enrollment Period but have no late enrollment penalty reason?

You can enroll during the General Enrollment Period (January 1 through March 31 of any year), and coverage begins July 1. However, you will owe a late enrollment penalty on Part B and Part D premiums for the rest of your life. The penalty is calculated based on how many months passed between the end of your Initial Enrollment Period and when you finally enroll.

Do I have to enroll in Part D if I do not take prescription medications?

You are not required to enroll in Part D, but if you go without it and later decide you need it, you will owe a late enrollment penalty. If you are certain you will never need prescription coverage, you can skip Part D. If you are unsure, it is usually safer to enroll during your Initial Enrollment Period to avoid the penalty.

If I am on Medicare, can I change my mind and go back to my employer plan?

Once you enroll in Medicare, you cannot switch back to your employer plan unless your employer offers a special enrollment period for employees who have already enrolled in Medicare. This is rare. Before you enroll in Medicare, confirm with your employer whether you will be able to return to their plan if you change your mind.