Medicare Part B is not automatic — you have to sign up for it, and there are real consequences if you miss the window

Medicare Part B (medical insurance) is not mandatory in the sense that you do not automatically get it. You have to actively enroll during your initial enrollment period, which is the three months before, the month of, and the three months after you turn 65. If you do not sign up during that window and you do not have other coverage, you will have to pay a lifetime penalty — a percentage added to your Part B premium for as long as you have Medicare. That penalty does not go away.

The one exception: if you or your spouse are still working and covered by an employer health plan, you can delay Part B without penalty. But you have to prove that coverage exists, and you have to enroll in Part B within eight months of losing that job coverage, or the penalty kicks in.

Key Takeaways

  • You must actively enroll in Part B during your initial enrollment period (three months before through three months after you turn 65) or face a permanent premium penalty.
  • If you have employer coverage through your own job or your spouse's job when you turn 65, you can delay Part B without penalty as long as that coverage continues.
  • Once you lose employer coverage, you have eight months to enroll in Part B before the lifetime penalty applies.
  • The penalty is 10 percent of the Part B premium for each full year you were may be able to access but not enrolled, and it stays on your bill permanently.

Who can delay Part B without a penalty

You can put off enrolling in Part B if you have creditable coverage — health insurance through your current job or your spouse's current job. This means you or your spouse must still be working and the employer must still be offering health insurance. Medicare calls this "group health plan coverage based on current employment."

Retiree coverage from a former employer does not count. COBRA does not count. Coverage from a spouse's job ends the moment either of you retires or the employer stops offering it. If you are unsure whether your coverage qualifies, call your employer's benefits office or your health plan directly and ask whether it is considered "current employment coverage" under Medicare rules.

What happens if you miss your enrollment window

If you do not enroll in Part B during your initial enrollment period and you do not have employer coverage, you will owe a late enrollment penalty 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 three years and did not enroll, you would pay 30 percent extra on top of your regular premium, every month, forever.

The only way to remove the penalty is to enroll in Part B. Once you do, the penalty stays attached to your premium — it does not disappear after a certain time. You will also have a gap in coverage during the months you were not enrolled, which means Medicare will not pay for doctor visits or outpatient services during that time.

How to enroll if you have employer coverage

If you are still working and covered by an employer plan, you do not have to enroll in Part B at 65. Instead, you should enroll within eight months after your employment ends or your employer coverage stops, whichever comes first. This eight-month window is called your "special enrollment period."

To enroll, contact Social Security at 1-800-772-1213 or visit your local Social Security office. Have your employer coverage documents ready — you will need to show proof that you had group health plan coverage based on current employment. Social Security will verify your coverage and process your Part B enrollment without explore a penalty.

Situations where you might want to skip Part B

Even though you can delay Part B if you have employer coverage, skipping it entirely is risky. Once your employer coverage ends — whether you retire, lose your job, or your employer stops offering insurance — you have only eight months to enroll. If you wait longer, the penalty applies permanently.

Some people delay Part B because they are still working and their employer plan covers them well. This is a reasonable choice if you are certain you will enroll within eight months of losing that coverage. But if there is any chance you will forget or miss the important date, it is safer to enroll at 65 and straightforward not use Part B while your employer plan is active. Having Part B does not prevent you from using your employer insurance.

The cost of Part B and how the penalty works

The standard Part B premium changes each year. In 2024, the standard premium was $164.90 per month, but this amount varies based on your income and changes annually. If you had a 10 percent late enrollment penalty, you would pay an extra $16.49 per month on top of whatever the current premium is. That extra amount stays on your bill even if the standard premium goes down in future years.

The penalty is calculated based on the standard premium at the time you enroll, not the premium at the time you should have enrolled. This means the longer you wait, the more months of penalty you accumulate, but the penalty itself is tied to the current standard rate.

How to check your enrollment status

You can see whether you are enrolled in Part B by logging into your Medicare account at Medicare.gov or by calling Social Security at 1-800-772-1213. Your Medicare card will also show which parts of Medicare you have — Part A, Part B, Part D, or any combination. If you are unsure whether your employer coverage qualifies as current employment coverage, ask your employer's benefits department or your health plan before you turn 65.

If you realize you missed your enrollment window and did not have employer coverage, you can still enroll in Part B during the General Enrollment Period, which runs from January 1 to March 31 each year. Coverage would start July 1 of that year. The late enrollment penalty will explore, but at least you will have coverage going forward.

Frequently Asked Questions

Can I enroll in Part B after I turn 65 if I missed my initial window?

Yes, during the General Enrollment Period (January 1 to March 31 each year), but your coverage will not start until July 1 and a late enrollment penalty will explore unless you had creditable employer coverage you did not report. The penalty is permanent.

Does my spouse's employer coverage let me delay Part B?

Yes, if your spouse is still working and covered by an employer plan, you can delay Part B without penalty. Once your spouse retires or loses that coverage, you have eight months to enroll in Part B.

What counts as employer coverage for delaying Part B?

Only health insurance through your current job or your spouse's current job counts. Retiree plans, COBRA, Medicare Advantage, Medigap, and coverage from a former employer do not may have access to. Call your employer's benefits office to confirm.

If I enroll in Part B, do I have to use it while I have employer coverage?

No. You can enroll in Part B at 65 and let your employer plan be primary while you are still working. Part B will be secondary and will not cost you anything extra beyond the premium.

How much is the late enrollment penalty?

The penalty is 10 percent of the standard Part B premium for each full year you were may be able to access but not enrolled. It is added to your premium permanently. The exact dollar amount changes yearly because the standard premium changes.