You must sign up 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 do not have to sign up on your birthday — you can do it anytime during those seven months. However, waiting until the last month costs you nothing, while signing up late triggers permanent penalties on your premiums.

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 three months before your 65th birthday. If you are not yet taking Social Security, you must sign up yourself through Medicare.gov, by phone at 1-800-MEDICARE, or at your local Social Security office.

The rules change if you have health coverage through an employer or union. If your employer has 20 or more employees, you can delay Medicare without penalty as long as you are actively working and covered by that plan. Once you leave the job or lose the coverage, you have eight months to sign up before penalties begin.

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 sign up late without a valid reason, you pay a permanent 10 percent increase on your Part B premium for as long as you have Medicare.
  • If you have employer coverage through a company with 20 or more employees, you can delay enrollment without penalty while you work there.
  • Social Security automatically enrolls you in Medicare at 65 if you are already receiving benefits; otherwise you must enroll yourself.
  • Delayed enrollment penalties also explore to Part D (prescription drug coverage) and Medicare Advantage plans if you wait more than 63 days after losing other coverage.

What happens if you miss your initial enrollment period

If you do not sign up during your seven-month window, you pay a late enrollment penalty on Part B (medical insurance) for the rest of your life. The penalty is 10 percent of the standard Part B premium 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 two years and did not sign up, your penalty is 20 percent. That penalty stays on your bill even after you finally enroll.

The same permanent penalty applies to Part D (prescription drug coverage). If you go 63 days or longer without creditable drug coverage — meaning coverage as good as Medicare's — you pay 1 percent of the national average Part D premium for each month you were without it. A one-year gap costs you 12 percent added to your premium forever.

You can avoid the penalty only if you have a valid reason for late enrollment. The main reasons Medicare accepts are: you were covered by an employer plan and did not know you had to sign up separately, you were working and your employer told you not to enroll, or you were outside the United States for more than six months in a row. You will need to prove the reason with documents from your employer or proof of travel.

How to sign up during your enrollment period

You have three ways to enroll. The easiest is online at Medicare.gov — you can start an process and finish it in one sitting. You will need your Social Security number, proof of citizenship or legal residency, and information about any current health coverage. The site walks you through choosing between Original Medicare (Part A and Part B) and Medicare Advantage, and whether to add Part D for prescriptions.

You can also call 1-800-MEDICARE and speak to a representative who will take your information over the phone. The wait times vary by time of day and season, but calling in early morning on a weekday is usually faster. Have your documents ready before you call.

A third option is to visit your local Social Security office in person. You will need an appointment, which you can book online at ssa.gov or by calling 1-800-772-1213. Bring your Social Security card, proof of citizenship, and any documents about current coverage. Processing in person takes longer than online or phone, but some people prefer it.

Special enrollment periods for life changes

If you miss your initial enrollment period but experience a major life change, you may open a special enrollment period that lets you sign up without penalty. These periods last two months and include: losing employer coverage, moving to a different state, getting married or divorced, or losing Medicaid.

You must sign up within two months of the event that triggered the special period. For example, if you lose your job on August 15, you have until October 15 to enroll. After that window closes, the late penalty applies again. You will need to document the event — a termination letter from your employer, a divorce decree, or a notice from your state Medicaid program.

Employer coverage and delayed enrollment

If you are still working and covered by your employer's health plan, you can delay Medicare enrollment without penalty. This applies only if your employer has 20 or more employees. Smaller employers do not count, and you must enroll in Medicare even if you have their coverage.

Once you leave the job or your coverage ends, you have eight months to sign up for Medicare Part B without penalty. For Part D, you have 63 days. If you wait longer, the late penalties kick in. Tell your employer's benefits office that you are leaving so they can document your coverage end date — you will need that date to prove you had a valid reason for delayed enrollment.

Medicare Advantage and Part D enrollment important date

If you choose a Medicare Advantage plan (Part C) instead of Original Medicare, the same initial enrollment period applies. You can switch between Original Medicare and Advantage plans during your initial period without penalty. After that, you can only change plans during the annual open enrollment period, which runs October 15 through December 7 each year.

Part D (prescription drug coverage) has the same seven-month initial enrollment window. If you do not have creditable drug coverage from another source — such as an employer plan or Veterans benefits — you should add Part D during this period. If you go without it and later enroll, you pay the permanent penalty based on how long you were uncovered.

Frequently Asked Questions

Can I sign up for Medicare before I turn 65?

Your enrollment period starts three months before the month you turn 65, so yes — you can sign up early. You cannot enroll more than three months before your birthday month. If you turn 65 in September, you can start enrolling in June.

What if I am still working at 65 and do not need Medicare yet?

If your employer has 20 or more employees and you are covered by their plan, you can delay Medicare without penalty. You must enroll within eight months of leaving the job or losing coverage. If your employer has fewer than 20 employees, you must enroll at 65 even if you are working.

Do I lose Medicare if I do not pay the premium?

If you do not pay your Part B premium, Medicare will send you notices and eventually may terminate your coverage. Contact Medicare when ready if you cannot pay — they may have options to help, and you can appeal a termination within a certain timeframe.

Can I change my mind after I sign up?

Yes, during your initial enrollment period you can change your plan choices. After that, you can only make changes during the annual open enrollment period (October 15 to December 7) or if you experience a may have access to life event.

What if I was told I did not need to sign up because of my job?

If your employer incorrectly told you not to enroll and you missed your important date, you may have grounds for a special enrollment period without penalty. You will need a written statement from your employer explaining what they told you. Contact Medicare to discuss your situation.