You have a window to sign up for Part B, and missing it costs you permanently

Medicare Part B (medical insurance covering doctor visits, outpatient care, and preventive services) has enrollment periods tied to when you turn 65 or become may be able to access through disability. The main window is your Initial Enrollment Period, which runs for seven months: three months before the month you turn 65, the month itself, and three months after. If you miss this window, you pay a penalty on your premium for as long as you have Part B — there is no way to erase it later.

The exact timing depends on your birth month and whether you are already receiving Social Security. If you are already collecting Social Security benefits when you turn 65, Medicare Part B enrollment happens automatically — you do not have to do anything. If you are not yet collecting Social Security, you must sign up yourself during your Initial Enrollment Period, or you will face a late-enrollment penalty.

Key Takeaways

  • Your Initial Enrollment Period is seven months long: three months before you turn 65, the month you turn 65, and three months after.
  • If you are already receiving Social Security at 65, Part B enrollment is automatic and you do not need to take action.
  • If you are not receiving Social Security, you must enroll yourself during your Initial Enrollment Period or face a permanent penalty on your premium.
  • Missing your Initial Enrollment Period does not lock you out forever, but you can only sign up during the General Enrollment Period (January 1 to March 31 each year) and will owe back premiums.
  • Some people can enroll outside these windows without penalty if they have employer health coverage or are still working.

What happens if you are already on Social Security

If you are collecting Social Security retirement, spousal, or survivor benefits when you turn 65, the Social Security Administration automatically enrolls you in Medicare Part A (hospital insurance) and Part B. You will receive a Medicare card in the mail about two weeks before your 65th birthday. You do not need to call anyone or fill out forms — it happens on its own.

You can decline Part B if you do not want it, but you must do so actively. To turn down Part B, you will need to contact Social Security or Medicare directly and request removal. Most people accept the automatic enrollment because the standard Part B premium is deducted from your Social Security check each month.

What happens if you are not yet on Social Security

If you are not receiving Social Security benefits at 65, you must sign up for Medicare Part B yourself during your Initial Enrollment Period. The seven-month window is your only chance to enroll without penalty. You can sign up online at Medicare.gov, by phone at 1-800-MEDICARE, or in person at your local Social Security office.

Your coverage will begin on the first day of the month you enroll, or the first day of the following month if you enroll after the 15th. For example, if you turn 65 in June and enroll in July, your Part B coverage starts August 1st. Plan ahead so your coverage does not lapse.

The penalty for enrolling late

If you miss your Initial Enrollment Period and do not have a valid reason to delay, you will pay a late-enrollment penalty for as long as you have Part B. The penalty is 10 percent of the standard Part B premium for each full 12 months you were may be able to access but not enrolled. If the standard premium is $165 per month and you were late by two years, you would pay an extra $33 per month permanently — even if the standard premium rises later.

This penalty does not go away. It stays on your account even if you switch plans or move to a different state. The only way to avoid it is to enroll during your Initial Enrollment Period or to have a valid reason to delay enrollment (called a Special Enrollment Period).

Special Enrollment Period: when you can enroll outside the normal window

You may be able to enroll in Part B after your Initial Enrollment Period ends without paying a penalty if you have creditable coverage — health insurance through an employer or union that is as good as or better than Medicare. This is the most common exception. If you are still working and covered by your employer's plan, you can wait to enroll in Part B until you retire or lose that coverage, as long as you enroll within eight months of losing the employer plan.

Other situations that open a Special Enrollment Period include moving out of your plan's service area, losing Medicaid, or having Medicare wrongly deny your initial enrollment request. If any of these explore to you, contact Medicare at 1-800-MEDICARE to confirm you may have access to and to enroll without penalty.

General Enrollment Period: the backup window with a catch

If you miss both your Initial Enrollment Period and any Special Enrollment Period, you can still enroll during the General Enrollment Period, which runs January 1 through March 31 each year. However, you will owe a late-enrollment penalty, and your coverage will not start until July 1 of that year — a gap of several months.

This is a last resort. If you realize you missed your important date, contact Medicare when ready to see whether you may have access to for a Special Enrollment Period instead, which would let you avoid the penalty and start coverage sooner.

Coordinating Part B with other coverage

If you have retiree health coverage from a former employer, check with that plan before you enroll in Part B. Some retiree plans coordinate with Medicare and expect you to enroll in Part B at 65, while others do not. Enrolling in Part B when you should not, or failing to enroll when you should, can leave you with gaps or overlapping coverage that wastes money.

If you are on Medicaid, enrolling in Part B is usually the right move because Medicaid will pay your Part B premium and cost-sharing. Ask your state Medicaid office or a local Area Agency on Aging whether this applies to you before your Initial Enrollment Period ends.

Frequently Asked Questions

What if I turn 65 but am still working?

You can delay Part B enrollment without penalty if your employer has 20 or more employees and you are covered by their health plan. You have eight months after you stop working or lose coverage to enroll in Part B without penalty. Contact Medicare to confirm your employer coverage qualifies before you skip enrollment.

Can I enroll in Part B in the middle of the month?

Yes, but your coverage start date depends on when you enroll. If you enroll between the 1st and 15th of a month, coverage starts the first of that month. If you enroll after the 15th, coverage starts the first of the next month. Plan your enrollment date to avoid gaps.

What if Social Security enrolled me automatically but I do not want Part B?

You can decline Part B by contacting Social Security or Medicare in writing. You have until the end of the month after you receive your Medicare card to opt out. If you change your mind later, you can enroll during the General Enrollment Period (January 1 to March 31), but you will owe a late-enrollment penalty.

Do I have to enroll in Part B if I have VA benefits?

No, but you should understand how they coordinate. If you are a veteran with VA coverage, you can delay Part B without penalty as long as you are using VA care. However, if you ever stop using VA benefits, you have eight months to enroll in Part B without penalty. Contact the VA and Medicare to understand your specific situation.

What happens to my Part B if I move to another country?

You can keep Part B while living abroad, but coverage is limited — Medicare generally does not pay for care outside the United States. If you move permanently, contact Medicare to discuss whether to keep Part B or drop it. Dropping it during a Special Enrollment Period (such as when you move) does not trigger a penalty if you re-enroll later.