An elderly female hand holds a mock United States government Medicare Health Insurance card.

Medicare Enrollment Periods

Each Medicare enrollment period offers different benefits for beneficiaries to enroll. Whether you are new to Medicare or wish to change your Medicare elections, understanding each enrollment period is essential.

Medicare enrollment periods can be confusing because different enrollment periods have different dates for various purposes. There are many enrollment periods for people signing up for Medicare benefits for the first time. When you are new to Medicare, you may not need to apply for benefits. You could be automatically enrolled in Medicare coverage if you meet a few requirements.

If you are receiving Social Security retirement benefits four months before you turn 65, you will automatically be enrolled in Original Medicare. Thus, you will not need to enroll yourself in Medicare Part A and Part B. If you are receiving Social Security Disability Insurance (SSDI) you will automatically be enrolled in Original Medicare upon your 25th month of SSDI payments.

If you do not qualify for automatic enrollment, but wish to enroll, you may use your Initial Enrollment Period and begin your Medicare enrollment in Part A, B, or both with Social Security Administration.

Initial Enrollment Period for New Medicare Beneficiaries

Your Initial Enrollment Period (IEP) for Medicare is a seven-month period that allows you to enroll in Medicare Part A and Medicare Part B. This enrollment period begins three months before your 65th birthday or three months before your 24th Social Security disability check, whichever comes first.

During your Initial Enrollment Period, you can enroll in both Part A or Part B of Original Medicare; you can enroll in just Part A and opt to delay Medicare Part B; or you can enroll in just Part B and not Part A because you have a Part A premium you do not wish to or cannot afford. For most, enrolling in Medicare Part A makes sense because for most it has a $0 monthly premium. However, if you have group health coverage due to your or your spouse’s active employment, it is not uncommon to delay Medicare Part B enrollment.

The Initial Enrollment Period begins three months before your Medicare enrollment qualifying event, the month of, and ends three months after your qualifying event. For most, this enrollment period happens around their 65th birth month.

For example, if you turn 65 on June 2, your enrollment period begins on March 1 and ends on September 30. Those with birthdays on the first of the month are considered 65 the month before.

If you enroll in Medicare during the three months before your 65th birthday, your Original Medicare benefits will go into effect on the first day of your birth month. If you enroll during your birth month your Part B coverage will begin on the first day of the following month. In 2023, if you enroll in the three months following your birth month, coverage will begin on the first day of the following month. Part A benefits, however, will go into effect retroactively up to 6 months but no sooner than ones 65th birth month. This is only true for those who have premium-free Part A. If you have a Part A premium the timing would match your Part B effective date.

Initial Enrollment Period for Individuals on Medicare Before 65

If you receive Medicare benefits before age 65 due to a disability, you will receive another Initial Enrollment when you turn 65.

For example, if you become eligible for Medicare at age 57 due to a disability and refused Part B at that time, you will be able to enroll for Part B at age 65 with no late enrollment penalties.

This additional Initial Enrollment Period runs the same seven-month period starting three months before the 65th birth month.

During any IEP, there is a parallel initial enrollment period for Medicare Advantage Plans and Medicare Part D plans. Additionally, for those who do not want Medicare Advantage, there is a Medigap Supplement open enrollment period that is tied to the start of Medicare Part B. When Part B is first started you have 6 months to purchase a Medigap plan to cover your Original Medicare out-of-pocket costs.

Special Enrollment Period in Medicare

  • Part B (and Premium Part A)
  • Part D
  • Managed Medicare

One of the most complicated Medicare enrollment periods is the Special Enrollment Period (SEP). Not all Medicare beneficiaries qualify for a SEP, and those who do will need to prove their qualification.

Part B – The most common reason for delaying Original Medicare coverage is because you have employer coverage in place at the time you turn 65 and afterward (not including retiree or COBRA coverage).

You would have a Part B (or Premium Part A) Special Enrollment Period starting at 65 as long as you or your spouse have employment rights (e.g. actively working) and due to that employees are covered by the group health

After the month you or your spouse’s employment ends or the month your employer group health plan coverage ends, whichever happens, sooner, then your Special Enrollment Period will close eight months later.  If you regain both employment and group health plan coverage from that employment, however, within those eight months, then your SEP will remain open.

Part D – If you already have Part A or B, but you had other creditable drug coverage that ended, for example from your employer, you will have a 63-day Special Enrollment Period to enroll in a Medicare Part D plan or a Medicare Advantage Plan that includes Part D (MA-PD). It is important to enroll in Medicare Part D  once you lose employer drug benefits to avoid paying the Medicare Part D late enrollment penalty.

Additionally, if you are in a Medicare Advantage or Medicare Part D plan, and experience a life-changing event you will often qualify for a Special Enrollment Period to make a change to your plan.

These life-changing events include:

  • Moving out of your plan’s service area
  • Your plan no longer services your area
  • You move in or out of a nursing home
  • You lose or gain Medi-Cal coverage
  • You become approved (or lose) Extra Help benefits

General Enrollment Period for People Who Miss Enrolling During Both the IEP or SEP

Suppose you miss enrolling in Original Medicare during your Initial Enrollment Period and do not have coverage due to employment that would qualify you for a Special Enrollment Period. In this case, you will need to wait until the General Enrollment Period (GEP) to enroll in Original Medicare.

The GEP runs annually from January 1 to March 31. When you enroll during this time, your coverage will go into effect on the 1st of the next month. Example: You apply in February; your benefits would be effective March 1.

Keep in mind, when you apply for Original Medicare during the General Enrollment Period, you may be responsible for paying a Premium- Part A and/or Part B late enrollment fee. This depends on how long you delayed enrolling when you could have enrolled in SEP. We recommend that you enroll in Medicare using either your IEP or SEP if you have one to avoid paying the late enrollment penalty.

Are There Enrollment Periods for Medicare Supplement (Medigaps) Plans?

Your Medicare Supplement Open Enrollment Period begins the 1st day of the month your Medicare Part B becomes effective. This is a six-month enrollment period that grants you a guaranteed-issue right for any Medicare Supplement (Medigap) plan you wish to enroll in. However, many carriers allow you to enroll in a Medicare Supplement plan up to two months before your Medicare Part B start date.

A Medicare Supplement plan is essential for Medicare enrollees who wish to pay as little out-of-pocket costs as possible for their healthcare coverage. Medicare Supplement plans cover the costs that Medicare Part A and Part B leave behind, eliminating the high expenses associated with Medicare coverage.

Enrolling in Medigap during a guaranteed-issue period is important. Especially if you have pre-existing conditions that could result in denial of your policy in the future.

If you miss your Medicare Supplement Open Enrollment Period, you can still apply for Medigap coverage throughout the year. However, there is a chance the application can be denied due to health issues that come up in underwriting.

Also, if you sign up for a Medicare Advantage plan during your IEP, you have 12 months to try the Medicare Advantage plan out. If within 12 months you are not happy, you have a guaranteed issue right to a Medigap.

Finally, once you do have a Medigap, it can be switched to another Medigap at any time. To ensure a guarantee issue, however, use the Birthday rule, which prevents underwriting questions when you switch on your birthday and up to 60 days after. The guarantee only exists when switching to a Medigap Plan with equal or fewer benefits.

Are There Enrollment Periods for Medicare Advantage Plans?

An alternative to Original Medicare is Managed Medicare in the form of Medicare Advantage plans.

Medicare Advantage plans are offered through private insurance companies and offer additional benefits to Original Medicare coverage. Often, these plans provide dental, hearing, vision, and drug coverage as well as gym memberships to enrollees. On the other hand, these plans tend to have prior authorization requirements, and unavoidable copays and are more restrictive than Original Medicare.

To enroll in a Medicare Advantage plan, you will want to utilize your Medicare Advantage plan’s Initial Enrollment Period. Remember, you must be enrolled in Original Medicare Part A and B to enroll in a Medicare Advantage plan.

If your Part B were delayed, and you use a SEP or GEP to sign up for and have Part B (and Part A already), then you would have three months before Part B starts to enroll in a Medicare Advantage plan.

If you miss your Medicare Advantage plan’s Initial Enrollment Period, you will have to wait until the Annual Enrollment Period to enroll in a Medicare Advantage plan for the following year.

Annual Enrollment Period for Medicare

The Annual Enrollment Period (AEP) for Medicare occurs each year from October 15 to December 7. This AEP allows Original Medicare enrollees to make several changes to their coverage.

These changes include:

  • Switching from Original Medicare to Medicare Advantage
  • Go from Medicare Advantage to Original Medicare
  • Switch from one Medicare Advantage plan to another
  • Enroll, change, or drop your Medicare Part D prescription plan

Suppose you use the AEP to return to Original Medicare from Medicare Advantage. In this case, you can then enroll in a Medicare Supplement plan to lower or eliminate your Original Medicare out-of-pocket costs. This plan will begin on January 1 of the following year. However, there is a chance the Medicare Supplement plan application can be denied due to underwriting unless there’s a guaranteed-issue right.

How to Get Help Understanding Medicare Enrollment Periods

It is essential to enroll in Medicare while you have a valid enrollment period. Missing these enrollment periods can lead to late penalties, lack of coverage, or denial of coverage in the future.

To ensure you enroll in the right Medicare plan for you at the right time, we have a team of Health Insurance Counseling & Advocacy Program (HICAP) counselors registered with the California Department of Aging. They are available to help at every step of the Medicare enrollment process. Whether you wish to enroll in a Medicare Part D plan, Medicare Advantage, or a Medicare Supplement plan.

HICAP Counselors do not sell, endorse, and are not affiliated with any insurance companies. Our goal is to inform and educate the community so you can make an informed decision on something as important as your Medicare healthcare insurance.


Not sure where to begin?

For an appointment, contact our Community Resource Specialists at (408) 350-3200, option 1.

For Medicare-related questions, complete the HICAP Interest Form.

This project was supported by the Administration for Community Living (ACL), U.S. Department of Health and Human Services (HHS) as part of a financial assistance award totaling $94,686 with 100% funding by ACL/HHS. The contents are those of the author(s) and do not necessarily represent the official views of, nor an endorsement, by ACL/HHS, or the U.S. Government.