Quick Answer:
There are four Medicare Advantage plan enrollment periods: the Initial Coverage Election Period (around your 65th birthday), the Annual Enrollment Period (October 15–December 7, effective January 1), the Medicare Advantage Open Enrollment Period (January 1–March 31, for a one-time plan change), and Special Enrollment Periods (triggered by qualifying life events). Missing these windows can lead to penalties or a gap in coverage.
Enrollment periods are vitally important for Medicare beneficiaries to understand and keep track of. Missing one can cause you to be penalized, and you could miss out on coverage. Here's a breakdown of the four Medicare advantage plan enrollment period windows, straight from what applies to Part C plans.
The Four Medicare Advantage Enrollment Periods
Once you confirm you're eligible for Medicare Advantage, there are four Part C enrollment periods during which you can enroll or make changes. You may not qualify for all of them, but each is important to understand.
1. Initial Coverage Election Period (ICEP)
Around the time of your 65th birthday, you have an Initial Enrollment Period during which you can enroll in Original Medicare - Parts A and B - and a Part D prescription drug plan.
The Initial Coverage Election Period for Medicare Advantage works similarly. It begins three months prior to your 65th birthday. Unlike the standard Initial Enrollment Period, the ICEP ends on the last day of the month before you enroll in Medicare Part B, or on the last day of your Initial Enrollment Period - whichever is later.
2. Annual Enrollment Period (AEP)
If you miss your Initial Coverage Election Period, your next opportunity to enroll in a Medicare Advantage plan is during the fall Annual Enrollment Period, which occurs annually from October 15 to December 7. Any enrollments made during this window become effective January 1 of the following year.
During AEP, you can:
- Switch from one Medicare Advantage plan to another
- Switch from Original Medicare to Medicare Advantage
- Switch from Medicare Advantage back to Original Medicare
- Review and make changes to a Part D prescription drug plan
No matter which changes you make, your new coverage becomes effective on January 1.
3. Medicare Advantage Open Enrollment Period (OEP)
If you missed the Annual Enrollment Period and want to make changes to your current plan, you can use the Medicare Advantage Open Enrollment Period, which runs every year from January 1 to March 31. During this window, you can make a one-time change to your current Medicare Advantage plan.
This period does not allow beneficiaries without a Medicare Advantage plan to enroll in one for the first time - it's only for those already enrolled in a Part C plan. Current plan holders can also choose to switch back to Original Medicare during this time.
4. Special Enrollment Periods (SEP)
Certain qualifying events allow beneficiaries to enroll in a Medicare Advantage plan or change their current one outside the standard windows, at any time of year. Qualifying situations on the site's list include:
- Relocation - moving to a new service area opens an SEP starting the month before your move and lasting two months after.
- Dual Eligibility - becoming eligible for both Medicare and Medicaid allows changes once per quarter for the first three quarters of eligibility.
- State Pharmaceutical Assistance Program - in participating states, a Part D change once per calendar year, separate from AEP.
- Weather-Related Emergency or Major Disaster - a FEMA-declared disaster opens an SEP starting at the time of the disaster, lasting four months.
- Institutionalized Individuals - those in nursing homes, rehab or psychiatric hospitals, or long-term care facilities qualify, with skilled nursing admission opening a window through two months post-discharge.
- Special Needs Plans - beneficiaries with chronic conditions such as ESRD, cancer, or dementia may qualify where the plan is available.
Trial Period and Trial Right
Medicare Advantage plans include a trial period. Enrolling during your ICEP grants a 12-month trial to disenroll and switch back to Original Medicare, plus 63 days of guaranteed issue rights to re-enroll in a Medicare supplement without being denied for a pre-existing condition. "Trial right" works similarly for those who dropped a supplement to try Medicare Advantage, usable only the first time. The guaranteed-issue supplement is generally the one you left, unless it's no longer offered - in which case Plans A, B, D, G, K, or L become available instead.
Choosing a Plan Type: HMO, HMO-POS, and Others
Once you've confirmed your enrollment window, you'll also need to decide on a plan type. HMO-POS insurance combines a standard HMO network with a "point of service" option, giving flexibility to see out-of-network providers at a higher out-of-pocket cost - useful for beneficiaries who travel.
If your plan also includes prescription drug coverage, it functions as an MAPD (Medicare Advantage Prescription Drug) plan. MAPD enrollment follows the same windows above, and any beneficiary already enrolled in Parts A and B is eligible, except those diagnosed with End-Stage Renal Disease. For a full breakdown of how these plans work, their costs, and provider network options, see our MAPD plans guide.
Medicare plans in California - including medicare supplement plans California residents may also be weighing - aren't available in every area, so confirming what's offered where you live is a useful step before enrolling.
Getting Enrollment Assistance
A licensed agent at California Medicare Agency can help you choose the right type of Medicare policy by understanding your lifestyle and healthcare needs, comparing options from multiple carriers, assisting with enrollment paperwork, and providing support during key enrollment periods, all at no cost to you.
Top 5 FAQs
1. What are the four Medicare Advantage enrollment periods?
The Initial Coverage Election Period (around your 65th birthday), the Annual Enrollment Period (October 15–December 7), the Medicare Advantage Open Enrollment Period (January 1–March 31), and Special Enrollment Periods, which apply when a qualifying event occurs.
2. Can I enroll in a new Medicare Advantage plan during the January–March Open Enrollment Period?
No. This period only allows a one-time change for beneficiaries already enrolled in a Medicare Advantage plan - it's not available to those trying to enroll in Part C for the first time.
3. What happens if I disenroll from Medicare Advantage during my trial period?
If you enrolled during your Initial Coverage Election Period, you have a 12-month trial period to switch back to Original Medicare, plus 63 days of guaranteed issue rights to re-enroll in a Medicare supplement plan without being denied for a pre-existing condition.
4. What qualifies someone for a Special Enrollment Period?
Events such as relocating to a new service area, becoming dually eligible for Medicare and Medicaid, a FEMA-declared disaster, moving into or out of an institution like a nursing home, or having a qualifying chronic condition for a Special Needs Plan.
5. What's the difference between HMO-POS insurance and a standard HMO in Medicare Advantage?
HMO-POS insurance adds a "point of service" option to a standard HMO network, allowing some out-of-network coverage at a higher out-of-pocket cost - offering more flexibility than a standard HMO, which generally only covers in-network care.
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