What to Know About the Medicare Enrollment Timelines

Medicare has specific timelines that limit when you can enroll in a plan, or change plans, based on your age and the time of the year. To help ensure you do not miss a window of opportunity, it is essential to become familiar with your enrollment periods and know when you are allowed to enroll and/or make changes to the different parts of Medicare.

Initial Enrollment into Medicare Part A and B:

This is when you first sign up for Medicare. You can enroll in Medicare three months prior to, the month of, and three months after the month you turn 65. Medicare coverage always begins on the first day of a month.

Initial Enrollment into a Medigap plan (Supplemental Plan):

Depending on how you choose to receive Medicare coverage, you can also purchase a Medigap Supplemental plan during the seven-month Initial Enrollment Period.

During that time, you can buy any Medigap policy sold in your state and receive guaranteed enrollment, even if you have health problems. This period automatically starts the first month you have Medicare Part B (Medical Insurance) when you're 65 or older. Once you purchase the plan, coverage will start on the first day of the following month.

You can’t enroll in a Medicare Supplemental plan unless you have enrolled in Medicare Parts A and B and have your Medicare ID number. And, if you want your Medigap coverage to start when your Part B becomes effective, it’s important to apply for your Medigap plan at least 15 days before your Part B effective date.

Initial Enrollment into Part D (Prescription Drug Coverage)

Medicare Drug Plans (Part D) have the same Initial Enrollment Period as Part A and B. You cannot enroll in a Medicare Part D stand-alone drug plan unless you have enrolled in Medicare Parts A and B and have your Medicare ID number.

Initial Enrollment into Medicare Part C (Medicare Advantage)

Medicare Advantage plans allow you to enroll during a seven-month window surrounding your 65th birthday, same as above. If the plan does not include drug coverage, you can also enroll in a Part D plan up to three months before the month you turn 65, and three months after you turn 65 (as long as you are already enrolled in Medicare Parts A and B.)

You can’t enroll in Medicare Part C unless you have enrolled in Medicare Parts A and B and have your Medicare ID number. If you enroll in a Medicare Advantage plan, you cannot enroll in a Medicare Supplemental Plan.

Late Enrollment Penalties for Part B Medicare

If you did not enroll in Medicare when you are first eligible, and you did not qualify for a special enrollment period, you will pay an extra 10% in your Part B premium for each year you were not enrolled after 65. This 10% penalty is added to your monthly Part B premium for the rest of your life.  Also, this penalty is not a one-time late fee, it will be applied to every month's premium for as long as you have Part B coverage.

Late Enrollment Penalties for Part D Medicare

You may have a late enrollment penalty for Part D (drug coverage) plans if you did not join a part D plan when you first enrolled in Medicare, and you went 63 days or more without creditable drug coverage. The penalty is an extra 1% for each month (12% a year) that you were eligible for Part D coverage and didn’t have creditable coverage. The penalty is added to your monthly premium and is not a one-time late fee. It will be applied to every month's premium for as long as you have Part D coverage, even if you change plans.

Your HealthPlanning Analysis will provide information to guide your enrollment timelines to avoid Late Enrollment Penalties.

Special Enrollment Period

There are a few special situations that allow you to delay your enrollment into Medicare and sign up at a later date without paying a late enrollment penalty. It’s very important for you to confirm that you will qualify for a Special Enrollment Period before you miss your Initial Enrollment window in order to avoid any late enrollment penalties. If your circumstances do qualify for a Special Enrollment Period, your coverage starts the first day of the month after your application has been accepted. The amount of time you have to sign up depends on the situation that qualified you for a Special Enrollment Period. One example would be if you were still employed and had qualifying health coverage through your employer. In this case, you are able to enroll up to eight months after your employer plan terminates for medical coverage but only 60 days for prescription drug coverage.

Annual Enrollment or General Enrollment

If you missed your Initial Enrollment Period, and you do not qualify for a Special Enrollment, then you won't be able to sign up for Medicare until the Annual or General Medicare Enrollment Period, which is January 1st – March 31st. If you sign up during this time, your coverage will start the first day of the month after you enroll. Enrolling in Medicare during the General Enrollment Period means you might have to pay a Part B late enrollment penalty. Social Security will calculate this penalty if you aren’t able to provide evidence of past coverage.

Open Enrollment

For Medicare plans

During the Open Enrollment Period, you can make changes to your existing Medicare plans provided by commercial insurers (Medigap plans, prescription drug plans, and Medicare Advantage plans), however, it’s important to carefully evaluate the changes you want. Some changes can be made relatively easily, like changing your prescription drug plan or changing from one Medicare Advantage Plan to another. Others (changing from a Medicare Advantage plan to a Medigap plan or from one Medigap plan to another) might require medical underwriting (questions regarding your health) and aren’t guaranteed after your initial Medicare enrollment.

For Part D or Medicare Advantage plans

If you want to change or drop your Part D drug plan, or Medicare Advantage plan, you can do that between October 15th and December 7th of each year. Those changes will take effect on January 1st of the following year. There is an additional period between January 1 and March 31 when you can also change from one Medicare Advantage plan to another. If you make a change during this time, your new Medicare Advantage coverage will start the first day of the month after your new plan receives your request for coverage. If you plan on changing from a Medicare Advantage plan to a Medigap Supplemental plan or visa versa, read this article on guaranteed trial rights.

With any of the enrollment windows above, it is imperative that you verify your personal situation to ensure you do not receive a late enrollment penalty, or worse, have a gap in coverage. Caribou’s HealthPlanning Analysis is able to help with plan reviews, enrollment dates, and understanding your options.

Learn More:

When does Medicare coverage start? | Medicare.gov

When can I join, switch, or drop a plan? | Medicare.gov

Do I have to enroll in Medicare at age 65 if I am already collecting Social Security? | AARP

Top 5 things you need to know about Medicare Enrollment | CMS.gov

When can I join a Part D prescription drug plan — or switch plans if I already have coverage? | AARP

Last Revised February 21, 2023