Who must enroll in Medicare and who does not have to

You are required to enroll in Medicare if you are a U.S. citizen or permanent resident and you turn 65. There is no way around this requirement — you cannot straightforward decline Medicare and keep working on your employer's health plan indefinitely. However, there are important exceptions and timing rules that change what "required" means in practice.

If you are still working at 65 and your employer has 20 or more employees, you do not have to enroll in Medicare Part B (medical insurance) right away. You can delay Part B without penalty as long as you stay covered by your employer's plan. Part A (hospital insurance) is different — you must enroll in Part A at 65 even if you are working, though you will not pay the premium if you or your spouse paid Medicare taxes for at least 10 years.

If your employer has fewer than 20 employees, Medicare becomes your primary insurance at 65, and you should enroll in Part B to avoid gaps in coverage. Self-employed people and those whose spouses are self-employed face the same rule as those at small employers.

Key Takeaways

  • You must enroll in Part A at 65 if you are a U.S. citizen or permanent resident, but you will not pay a premium if you or your spouse paid Medicare taxes for 10 years.
  • Part B enrollment can be delayed without penalty only if you are still working and covered by an employer plan with 20 or more employees.
  • If you miss your enrollment window and do not have a may have access to reason, you will pay a permanent penalty on your Part B premium for as long as you have Medicare.
  • Certain groups — including federal employees, railroad retirees, and some people with disabilities — have different enrollment rules and important date.
  • Your initial enrollment period is the three months before, the month you turn 65, and the three months after — a seven-month window total.

What happens if you do not enroll when you are supposed to

Missing your enrollment important date triggers a late enrollment penalty that stays with you permanently. For Part B, the penalty is 10 percent of the standard premium for each full year you were may be able to access but not enrolled. If you were may be able to access at 65 but did not enroll until age 68, you would pay an extra 30 percent on top of your Part B premium for the rest of your life.

Part A does not usually carry a late penalty if you enroll within two years of becoming may be able to access, but if you wait longer than two years, you will pay a penalty equal to 10 percent of the standard premium for twice the number of years you were may be able to access but not enrolled.

The only way to avoid this penalty is to have a may have access to reason — the most common being that you were covered by an employer plan. You will need to show proof of that coverage (usually a letter from your employer or a copy of your health plan documents) when you enroll. Other may have access to reasons include being a federal employee, a railroad retiree, or having end-stage renal disease or ALS.

Your initial enrollment period and how to use it

Your initial enrollment period runs for seven months: the three months before you turn 65, the month you turn 65, and the three months after. During this window, you can enroll in Part A and Part B without penalty, and your coverage can start as early as the first day of the month you turn 65.

Timing matters within this window. If you enroll before the month you turn 65, your coverage starts the first day of the month you turn 65. If you enroll during the month you turn 65, coverage starts the first day of the following month. If you enroll after the month you turn 65, coverage starts the first day of the month after you enroll.

You can enroll online at Medicare.gov, by phone at 1-800-MEDICARE, or in person at your local Social Security office. If you are already receiving Social Security benefits, you will be enrolled automatically in Part A and Part B three months before you turn 65 — you do not have to do anything unless you want to decline Part B.

Special enrollment periods for people with employer coverage

If you are still working and covered by an employer plan, you have a special enrollment period that extends eight months past the end of your employment or loss of coverage. This means you can enroll in Part B without penalty even if you miss your initial seven-month window, as long as you enroll within that eight-month window and can prove you had employer coverage.

You must enroll during this special period or lose the protection against late penalties. Waiting until age 70 or later, even if you had employer coverage the whole time, will not protect you if you do not enroll within the eight-month window. The proof you need is a letter from your employer stating the dates you were covered and the number of employees, or a copy of your health plan documents showing your coverage dates.

Medicare Part A versus Part B enrollment requirements

Part A and Part B have different rules, and understanding the difference matters. Part A covers hospital stays, skilled nursing care, hospice, and home health. Part B covers doctor visits, outpatient care, and medical equipment. You can enroll in one without the other, though most people eventually need both.

Part A has no monthly premium if you or your spouse paid Medicare taxes for at least 10 years. If you did not, the premium ranges depending on how many years of Medicare tax you paid. Part B always has a monthly premium, and the amount increases if you have higher income.

If you are still working at 65 with employer coverage, you can delay Part B but not Part A. Part A enrollment is automatic at 65 for most people, and you cannot decline it without losing your right to delay Part B penalty-free.

Groups with different enrollment rules

Federal employees who are covered by the Federal Employees Health Benefits Program (FEHB) can delay Part B without penalty while covered by FEHB, even after they turn 65. They have a special enrollment period that extends until eight months after they lose FEHB coverage or retire, whichever comes first.

Railroad retirees covered by the Railroad Retirement Board have their own enrollment timeline and rules. They should contact the Railroad Retirement Board directly rather than Social Security to understand their specific requirements.

People with end-stage renal disease or ALS have different enrollment rules and may be able to enroll in Medicare before age 65. People who are disabled and under 65 can enroll in Medicare if they have been receiving Social Security Disability Insurance (SSDI) for 24 months or have been on dialysis for three months.

What to do if you missed your enrollment important date

If you missed your initial enrollment period and do not have a may have access to reason, you can still enroll, but you will pay a late penalty. You can enroll during the general enrollment period, which runs from January 1 to March 31 each year. Coverage would start July 1 of that year.

Before you enroll, gather any documents that might count as a may have access to reason — employer coverage letters, proof of other health insurance, or documentation of a life event like losing a job. Even if you think you do not have a may have access to reason, it is worth asking when you enroll. Some people discover they do may have access to and can avoid the penalty.

If you need help understanding your specific situation, you can contact Medicare at 1-800-MEDICARE or visit your local Social Security office. State Health Insurance information Programs (SHIPs) also offer free counseling about Medicare enrollment and can help you figure out whether you have a may have access to reason to avoid penalties.

Frequently Asked Questions

Can I turn down Medicare and stay on my employer plan instead?

No. You must enroll in Part A at 65. However, if your employer has 20 or more employees and you are still working, you can delay Part B without penalty. Once you leave that job or lose coverage, you have eight months to enroll in Part B without a late penalty.

What if I do not think I have worked long enough to may have access to for Part A?

Contact Social Security before your 65th birthday to find out. If you do not have 10 years of Medicare tax contributions, you can still enroll in Part A but will pay a monthly premium. The amount depends on how many years you did contribute.

Do I have to enroll in Part D (prescription drug coverage) at 65?

Part D is optional, but if you go without it and later enroll, you will pay a permanent penalty unless you had other creditable drug coverage. The penalty is about 1 percent of the national average Part D premium for each month you were without coverage.

What counts as a may have access to reason to avoid the late penalty?

The most common may have access to reasons are employer coverage with 20 or more employees, federal employee coverage, railroad retirement, and certain disabilities. You will need to provide proof — usually a letter from your employer or a copy of your health plan documents showing your coverage dates.

If I am already getting Social Security, do I have to do anything?

No. You will be enrolled automatically in Part A and Part B three months before you turn 65. If you do not want Part B, you must decline it in writing before your coverage starts. Contact Social Security if you want to decline.