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The dates when you can sign up or change

The dates when you can sign up for Medicare or change coverage. Fall Annual Enrollment and your first-time window use different rules, even when the months overlap.

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1

The first time you enroll

These windows are for signing up the first time, or for buying a Medicare Supplement (also called Medigap) when Part B starts.

  • When

    Initial Enrollment Period

    The 7 months around the month you turn 65.

    What is it for
    You are turning 65 and you do not have Medicare yet.
    Available changes
    Sign up for Part A and Part B. This is also the usual first chance to join a Medicare Advantage plan or a Part D plan.
    What is outside this window
    Not the fall Annual Enrollment. The month-by-month dates, and when job coverage may let you wait, are on The 7-month window.

  • When

    General Enrollment Period

    January 1 – March 31 each year.

    What is it for
    You missed Initial Enrollment, and you do not have a Special Enrollment Period from job coverage or another qualifying event.
    Available changes
    Sign up for Part A and Part B. Coverage usually starts the month after you enroll. A late penalty can apply.
    What is outside this window
    These are the same months as Medicare Advantage Open Enrollment, but that is a different window for people already in an Advantage plan.

  • When

    Medigap Open Enrollment

    The 6 months starting with the month Part B begins, if you are 65 or older.

    What is it for
    You want a Medicare Supplement to go with Original Medicare.
    Available changes
    Buy any Medicare Supplement letter sold in California without health questions.
    What is outside this window
    This is not Annual Enrollment, and it is not the California Birthday Rule. Under 65, the rule is different. Confirm with the company.
2

Already have Medicare

These windows are for changing a Medicare Advantage plan or a Part D plan you already have. You do not have to change.

  • When

    Annual Enrollment

    October 15 – December 7 each year. A change made then usually starts January 1.

    What is it for
    You already have Medicare and you want to join, switch, or drop Medicare Advantage or Part D.
    Available changes
    Change Medicare Advantage or Part D for the next year. You can also stay in the coverage you have.
    What is outside this window
    This is not a window to buy a Medicare Supplement without health questions.

  • When

    Medicare Advantage Open Enrollment

    January 1 – March 31 each year.

    What is it for
    You started the year in a Medicare Advantage plan.
    Available changes
    Make one change: switch to a different Advantage plan, or return to Original Medicare and join a Part D plan.
    What is outside this window
    This is not for someone who only has Original Medicare. It is also not the General Enrollment Period, even though the dates match.

This downloads a calendar file to your phone or computer. It does not change your coverage.

3

Already have a Medicare Supplement

This window is only for changing a Medicare Supplement you already have in California. It does not change a Medicare Advantage plan or a Part D plan.

  • When

    California Birthday Rule

    60 days starting on your birthday. Day one is your birthday, not the day before.

    What is it for
    You already have a Medicare Supplement (also called Medigap) in California.
    Available changes
    Apply for another Supplement with the same benefits, or fewer, generally without health questions. Some companies give more than 60 days. Use the notice from your company if it is longer.
    What is outside this window
    This is not Annual Enrollment. It is not a way to leave a Medicare Advantage plan. It does not let you move to a letter with more benefits, such as from Plan N to Plan G. Do not drop the policy you have until the new company says the new policy is issued.
4

Something in your life changed

A Special Enrollment Period does not have one set of dates. The event decides the months.

  • When

    Special Enrollment Period

    The months that belong to that event. This website cannot look them up.

    What is it for
    You lost job coverage, moved out of a plan’s area, had a change in Extra Help or Medi-Cal, your plan is ending, you are in a first-year trial right, or you moved into or out of a nursing home.
    Available changes
    Make the change that event allows, during the months that rule allows. Whether job coverage lets you delay Part B is on The 7-month window, not on this list.
    What is outside this window
    Do not guess the deadline. Write down the event and confirm the dates on Medicare.gov or by calling 1-800-MEDICARE (TTY 711).

Want the full story? Get my book. Medicare 2026: Choose the Right Plan & Avoid Costly Mistakes walks through how Medicare is built. It does not pick a plan.

Worksheet

Find My Enrollment Window

Which enrollment window am I in? See whether Initial Enrollment, General Enrollment, Annual Enrollment, Medicare Advantage Open Enrollment, a Medicare Supplement (also called Medigap), or a Special Enrollment Period may be open.

Read: Which enrollment window am I in?

Do you already have Medicare?
Which of these apply? Check any.
Has a Special Enrollment situation happened? Check any.

May be open on this date

  • Annual Enrollment (AEP)Open on this date

    October 15 – December 7, 2026

    This window is open. If you already have Medicare, you can join, switch, or drop a Medicare Advantage plan or a Part D plan for 2027. A change made by December 7, 2026 generally starts January 1, 2027. It is not the Medicare Advantage Open Enrollment Period, and it is not Medigap Open Enrollment.

    This downloads a calendar file to your phone or computer. It does not change your coverage.

A Special Enrollment Period may apply

  • Special Enrollment Period — 5-star planOpen on this date

    December 8 – November 30

    If a 5-star Medicare Advantage or Part D plan is offered where you live, you may switch to that plan once during this span. This form cannot see star ratings. Confirm on Medicare.gov.

Other windows are not open on this date
  • Initial Enrollment PeriodNot open

    The seven months around the month you first became eligible

    If you already have Medicare, this first window is behind you. A fall change uses Annual Enrollment.

  • Initial Coverage Election PeriodNot open

    When you first could join a Medicare Advantage plan

    If you already have Medicare, a later Advantage change uses Annual Enrollment, Medicare Advantage Open Enrollment, or a Special Enrollment Period.

  • General Enrollment PeriodNot open

    January 1 – March 31, 2026

    If you missed Initial Enrollment and you do not have a Special Enrollment Period, you can sign up for Part A and Part B during these dates. Coverage usually starts the month after you enroll, and a late penalty can apply. These months are also Medicare Advantage Open Enrollment, which is a different window.

    This downloads a calendar file to your phone or computer. It does not change your coverage.

  • Medicare Advantage Open EnrollmentNot open

    January 1 – March 31, 2027

    This window is not open on this date. It runs January 1 through March 31, 2027, and only for someone who is in a Medicare Advantage plan. It is not open during Annual Enrollment.

    This downloads a calendar file to your phone or computer. It does not change your coverage.

  • Medigap Open EnrollmentNot open

    Six months from the month Part B starts, if you are 65 or older

    Enter a Part B start date to see the dates. This is not Annual Enrollment and not the California Birthday Rule. Under 65, the rule is different.

  • California Medigap Birthday RuleNot open

    60 days starting on your birthday

    This window is only if you already have a Medicare Supplement in California. It is not a way to leave a Medicare Advantage plan.

  • Special Enrollment Period — job coverageNot open

    While the job coverage lasts, and typically 8 months after the job or the coverage ends, whichever is first

    Coverage from a current employer of 20 or more people, including a working spouse, may let you delay Part B. COBRA usually does not extend this window. Part D uses a shorter clock, often two months. Get the proof in writing. This is not a determination.

  • Special Enrollment Period — you movedNot open

    Often the month before the move through two months after it

    A move out of your plan’s service area can let you pick a new Medicare Advantage or Part D plan. The exact months depend on when you tell the plan. Confirm the dates for your move.

  • Special Enrollment Period — Extra Help or Medi-CalNot open

    Once a month, if you have Extra Help or Medicaid

    People with Extra Help, Medi-Cal, or a Medicare Savings Program may switch to Original Medicare and a stand-alone Part D plan, or switch stand-alone Part D plans, once a month. This does not let you join a new Medicare Advantage plan. Some people with full Medi-Cal can also join certain integrated Dual Special Needs Plans once a month. A government agency decides whether you qualify. This form does not.

  • Special Enrollment Period — your plan is endingNot open

    The dates in the letter from Medicare or the plan

    If your Medicare Advantage or Part D plan is leaving Medicare or leaving your area, the notice gives the window. Do not guess those dates from this form.

  • Special Enrollment Period — trial rightNot open

    During the first 12 months in a Medicare Advantage plan, in the situations Medicare allows

    In some first-year cases you can drop Medicare Advantage and return to Original Medicare, and you may have a right to buy a Supplement without health questions. There is more than one trial right. Confirm which one fits before you drop a plan.

  • Special Enrollment Period — nursing home or other institutionNot open

    While you live in a qualifying institution, and for up to two months after you leave

    A move into or out of a nursing home or similar institution can open a window to join or change a plan. The facility has to qualify. Confirm that on Medicare.gov.

Checking a box does not approve a Special Enrollment Period. Medicare or Social Security decides whether that situation qualifies. This is an estimate, not a decision from Medicare or Social Security. Confirm the window that fits on Medicare.gov or with Social Security.

2026 figures

Medicare eligibility date

See when Part A and Part B can start at 65, and your Initial Enrollment window.

Read: Month by month around 65

CalculatorPart B late enrollment penaltyEstimate the 10% Part B surcharge for each full 12-month delay.

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