You must enroll in 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. During this window, you can join Part A (hospital insurance), Part B (medical insurance), or both without penalty.

If you miss this window, you will pay a permanent penalty on your monthly premiums for as long as you have Medicare — unless you had may have access to coverage through an employer or union when you turned 65. The penalty is 10 percent of the Part B premium for each full year you delayed, and it compounds. Missing the important date by two years means a 20 percent penalty for life.

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 that changes each year. You do not have to enroll in Part B at 65 if you are still working and covered by your employer's health plan, but you will need to enroll within eight months of leaving that job to avoid the penalty.

Key Takeaways

  • Your Initial Enrollment Period runs for seven months: three months before, the month of, and three months after you turn 65.
  • If you miss this window and do not have employer coverage, you will pay a permanent 10 percent penalty on Part B premiums for each year you delayed.
  • Part A is usually free at 65 if you paid Medicare taxes for at least 10 years; Part B requires a monthly premium.
  • If you are still working at 65 and covered by your employer's health plan, you can delay Part B enrollment without penalty, but you must enroll within eight months of leaving that job.
  • You can enroll online at Medicare.gov, by phone at 1-800-MEDICARE, or in person at your local Social Security office.

What counts as employer coverage that lets you delay

If you or your spouse is still working at 65 and you have health insurance through that job, you can delay enrolling in Part B without facing a late penalty. This is called having creditable coverage. The coverage must be based on current employment — not retirement coverage, not COBRA, and not coverage through a spouse's former employer.

You have eight months from the date you or your spouse stops working or lose the employer coverage, whichever comes first, to enroll in Part B without penalty. If you wait longer than eight months, the 10 percent penalty applies. You should enroll during this eight-month window even if you plan to keep your employer plan alongside Medicare, because Medicare becomes your primary payer once you are enrolled.

If you are unsure whether your coverage counts as creditable, call your employer's benefits office or your health plan directly. They can tell you whether your plan meets Medicare's definition. Bring that answer with you when you enroll, because Social Security will ask.

How to enroll during your Initial Enrollment Period

You can enroll online, by phone, or in person. The online route is fastest: go to Medicare.gov, sign in with your Social Security number, and follow the enrollment steps. You will need your Social Security number, date of birth, and citizenship or immigration status. The process takes about 10 minutes.

If you prefer to enroll by phone, call 1-800-MEDICARE (1-800-633-4227). Representatives are available Monday through Friday, 8 a.m. to 8 p.m. Eastern time. Have your Social Security card or number ready. They can answer questions about Part A and Part B costs and coverage before you enroll.

You can also walk into your local Social Security office and enroll in person. Find your office at ssa.gov/locator. Bring your Social Security card, proof of citizenship or legal residency (passport, birth certificate, or green card), and proof of age. Offices are busiest early in the month and early in the week, so plan accordingly.

What happens if you miss your Initial Enrollment Period

If you do not enroll during your seven-month window and you do not have employer coverage, you enter a situation called late enrollment. You can still enroll in Part A and Part B, but you will owe a permanent penalty on top of your regular premiums.

The Part B penalty is 10 percent of the standard premium amount for each full 12-month period you were may be able to access but not enrolled. If you were may be able to access for three years and did not enroll, you owe a 30 percent penalty. This penalty stays on your bill for as long as you have Part B, even if you move to a different state or change plans.

The Part A penalty is smaller — 10 percent of the hospital insurance premium — but it also lasts for life. You can avoid the Part A penalty if you enroll within the first two years after your Initial Enrollment Period ends, but the Part B penalty has no such grace period.

If you realize you missed the important date, 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. This is a much longer wait than enrolling during your Initial Enrollment Period, when coverage can begin as early as the first day of the month you turn 65.

Special enrollment periods if your situation changed

If you missed your Initial Enrollment Period but you had a major life change — such as losing employer coverage, moving to a new state, or experiencing a change in your immigration status — you may be able to enroll without penalty during a Special Enrollment Period. These periods are usually 60 days long and must be used within a specific timeframe tied to your life event.

Losing employer coverage is the most common reason for a Special Enrollment Period. If you or your spouse lost group health insurance through work, you have 60 days from the date coverage ended to enroll in Part B without penalty. You must enroll during this 60-day window; if you wait until the General Enrollment Period, the penalty applies.

Other may have access to events include moving out of your health plan's service area, losing Medicaid coverage, or becoming a U.S. citizen or permanent resident. If you think you have a may have access to event, contact Social Security at 1-800-772-1213 or visit your local office. Bring documentation of the event — a letter from your employer, a notice from your health plan, or proof of your new immigration status.

Part A and Part B costs and what they cover

Part A covers inpatient hospital stays, skilled nursing facility care, hospice, and some home health services. Most people do not pay a monthly premium for Part A if they or their spouse paid Medicare taxes for at least 10 years. If you do not meet this requirement, you can still enroll and pay a monthly premium, which varies by how many years of work history you have.

Part B covers doctor visits, outpatient care, lab tests, imaging, and some preventive services. Everyone pays a monthly premium for Part B. The standard premium in 2024 is $164.90 per month, but it changes each year and may be higher if your income is above a certain level. You will see your exact premium when you enroll.

When you enroll in Part B, you will also be asked whether you want to enroll in Part D (prescription drug coverage) at the same time. Part D is optional but recommended if you take any medications. If you delay Part D enrollment beyond your Initial Enrollment Period, you will pay a penalty on your premiums for as long as you have Part D, similar to the Part B penalty.

Frequently Asked Questions

What if I turn 65 while I'm still working?

You can delay enrolling in Part B if you have health insurance through your current job. You must enroll within eight months of leaving that job or losing the coverage. Part A is still free at 65 if you meet the work history requirement, and you can enroll in it without affecting your employer plan.

Can I change my mind after I enroll?

Yes, but only during certain times. You have seven days from the date you enroll to cancel and restart your enrollment. After that, you can make changes during the Annual Enrollment Period (October 15 through December 7 each year), and changes take effect January 1. If you made a mistake during your Initial Enrollment Period, contact Social Security to see if they can correct it.

What if I was not a U.S. citizen when I turned 65?

You can enroll in Medicare once you become a U.S. citizen or permanent resident. Your Initial Enrollment Period starts the month you become a citizen or permanent resident, not the month you turned 65. Bring proof of your immigration status when you enroll.

Do I have to enroll in Part A if I only want Part B?

No. You can enroll in Part B alone. However, Part A is free for most people at 65, so it usually makes sense to take it even if you do not plan to use it right away. If you decline Part A during your Initial Enrollment Period, you can enroll later, but you may face a penalty.

What happens to my employer coverage once I enroll in Medicare?

Medicare becomes your primary payer once you enroll, meaning it pays first. Your employer plan pays second. You should keep your employer coverage if it is still available, because it can cover costs Medicare does not. Tell your employer's benefits office that you have enrolled in Medicare so they can coordinate payments correctly.