Medicare enrollment is required at 65 for most people, but the timing and consequences depend on your work status and other coverage

You must enroll in Medicare Part A (hospital insurance) and Part B (medical insurance) when you turn 65 if you are a U.S. citizen or permanent resident who has lived in the country for at least five years. However, if you are still working and covered by your employer's health plan, you can delay Part B enrollment without penalty — but Part A enrollment is automatic for most people at 65 and happens whether you want it or not.

The key rule is this: if you do not enroll in Part B when you first become may be able to access, you will pay a permanent 10% higher premium for each year you delayed. This penalty stays with you for life. Part A has no such penalty, but delaying it can create gaps in coverage that are hard to fix later.

If you have coverage through a current employer (yours or your spouse's), you have a window to delay Part B without penalty. This is called the Special Enrollment Period. You must enroll within eight months after your employment ends or your employer coverage stops, whichever comes first. Missing this window triggers the penalty.

Key Takeaways

  • Part A enrollment is automatic at 65 for most people; you do not have to do anything, but you should check that Social Security has the correct information.
  • Part B enrollment is your choice, but delaying it after age 65 costs you 10% more per month for the rest of your life unless you have employer coverage.
  • If you are still working and covered by your employer's health plan, you can delay Part B without penalty as long as you enroll within eight months after work ends.
  • Missing the eight-month window after employment ends means you pay the permanent penalty, even if you enroll years later.
  • You must actively enroll in Part D (prescription drug coverage) or face a penalty if you go without it for more than 63 days in a row.

How automatic enrollment works for Part A

Three months before you turn 65, Social Security sends you a notice in the mail. Part A enrollment happens automatically on the first day of the month you turn 65 — you do not need to sign anything or call anyone. Your Medicare card arrives in the mail about two weeks before your 65th birthday.

You should still check the information on your card. If your name, date of birth, or Social Security number is wrong, contact Social Security before your birthday to correct it. Mistakes on your card can delay claims or cause coverage problems later.

Part A covers hospital stays, skilled nursing facility care, hospice, and home health services. It does not cover doctor visits or outpatient care — that is what Part B is for.

Part B enrollment: when you must act and when you can wait

Unlike Part A, Part B requires you to make a choice. You enroll through Social Security, either online at ssa.gov, by phone at 1-800-772-1213, or in person at your local Social Security office. You have a seven-month window called your Initial Enrollment Period: three months before the month you turn 65, the month itself, and three months after.

If you enroll during this window, your coverage starts on the first day of the month you turn 65 (or the first day of the following month if you enroll in the month you turn 65 or after). If you miss this window and do not have employer coverage, your Part B coverage will not start until the following January, and you will owe the 10% penalty.

The penalty is calculated as 10% of the standard Part B premium for each full year you were may be able to access but not enrolled. If the standard premium is $165 per month and you delayed two years, your penalty would be 20% — an extra $33 per month for life. This penalty does not go away if you move to a different state or change plans.

Employer coverage and the eight-month rule

If you or your spouse is still working and you have health coverage through that job, you can delay Part B without penalty. This applies whether the employer has 20 or more employees or fewer than 20. The rule is the same: you have eight months after employment ends or coverage stops to enroll in Part B.

The eight months starts the month after your employment ends or the month your employer coverage ends, whichever is later. If you work until June 30 and your coverage ends June 30, your eight-month window runs from July through February. You must enroll by the end of February to avoid the penalty.

You do not need to enroll in Part B the moment you leave your job. Many people wait until their employer coverage actually ends, then enroll in Part B to start the following month. This creates a smooth transition with no gap. However, if you wait too long and miss the eight-month important date, the penalty applies even if you enroll later.

Part D enrollment and the 63-day rule

Part D is prescription drug coverage, and it is optional — but only if you have other creditable coverage. Creditable coverage means drug coverage that is at least as good as Medicare's. This includes employer plans, union plans, Veterans benefits, and some Medicaid plans.

If you do not have creditable coverage and you do not enroll in Part D when you first become may be able to access, you pay a penalty for each month you go without it. The penalty is 1% of the national average Part D premium for each month of delay. If you go without coverage for more than 63 days in a row, the penalty applies permanently.

You can enroll in Part D during your Initial Enrollment Period (the same seven-month window as Part B), during the annual Open Enrollment Period (October 15 to December 7), or if you lose creditable coverage. If you lose employer drug coverage, you have 63 days to enroll in Part D without penalty.

What happens if you miss enrollment important date

If you miss your Initial Enrollment Period for Part B and do not have employer coverage, you enter a General Enrollment Period that runs January 1 to March 31 each year. You can enroll then, but your coverage does not start until July 1, and you owe the permanent penalty.

There is no way to remove the Part B penalty once it is applied. It does not matter if you enroll later, move to a different state, or change Medicare plans — the penalty stays. The only exception is if you were working and had employer coverage that you did not know was not creditable, and you can prove it. This is rare and requires documentation.

For Part D, if you go 63 days or more without coverage and without creditable coverage, the penalty applies for as long as you have Part D. Like Part B, this penalty does not go away.

Medicare Advantage and Medigap: enrollment is still required

If you choose a Medicare Advantage plan (Part C) instead of Original Medicare, you still must be enrolled in Part A and Part B first. Medicare Advantage replaces Part B and includes Part A, so you cannot have one without the other. You enroll in Medicare Advantage during the same Initial Enrollment Period or during the annual Open Enrollment Period (January 1 to March 31).

If you choose a Medigap plan (supplemental insurance), you must also be enrolled in Part A and Part B. Medigap does not replace Medicare — it covers costs that Medicare does not, like copayments and coinsurance. You can enroll in Medigap anytime, but if you enroll more than six months after your Part B start date, the insurance company can charge you more or deny coverage for pre-existing conditions.

Frequently Asked Questions

Can I turn down Medicare and keep my employer coverage instead?

You can delay Part B if you have employer coverage, but Part A enrollment is automatic and you cannot refuse it. If you try to turn down Part A, you may lose your Social Security benefits. The best approach is to enroll in Part A and delay Part B until your employer coverage ends, then enroll in Part B within eight months.

What if I do not know whether my employer coverage is creditable?

Your employer or union should give you a notice each year stating whether your drug coverage is creditable. If you do not have this notice, ask your benefits department or HR office. If you cannot find out and you are worried about the Part D penalty, you can enroll in Part D and drop it later if you find out your coverage was creditable — you will not owe a penalty for the months you had Part D.

Do I have to enroll in Medicare if I am still working and do not need it yet?

Part A enrollment is automatic at 65 and you cannot stop it. Part B enrollment is your choice if you have employer coverage. However, you must enroll in Part B within eight months after your employment ends to avoid the permanent penalty, so delaying too long creates risk.

What if I enrolled in Part B but then went back to work?

You can keep Part B while working. Your employer coverage and Part B will coordinate, and you will not owe a penalty. However, if you enrolled in Part B before your employer coverage ended, you may have paid Part B premiums you did not need. You cannot get a refund, but you can drop Part B and re-enroll later without penalty as long as you re-enroll within eight months of leaving your job.

Can I enroll in Medicare before I turn 65?

No, with rare exceptions. You must be 65 or older, or you must be under 65 and have received Social Security Disability Insurance (SSDI) for 24 months, or have end-stage renal disease or ALS. If you have one of these conditions, contact Social Security to learn about your options.