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Medicare and ACA Enrollment Dates at a Glance

Every current Medicare and ACA Marketplace enrollment window in one place -- Annual Enrollment, Medicare Advantage Open Enrollment, Initial Enrollment, and ACA Open Enrollment -- with what each one lets you change.

Medicare3 min readReviewed 2026-09-17

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Short answer

Medicare's Annual Enrollment Period runs October 15 through December 7 each year, for coverage starting January 1. The Medicare Advantage Open Enrollment Period runs January 1 through March 31 for people already enrolled in a Medicare Advantage plan. ACA Marketplace Open Enrollment for 2027 coverage runs November 1, 2026 through January 15, 2027 in most states. Outside these windows, a qualifying life event can open a Special Enrollment Period.

Use this before you call.

Not sure which window applies to you? Call GetFastRates.com for a free, no-pressure review of your timing.

Check which window applies to you: Medicare Annual Enrollment, Medicare Advantage Open Enrollment, Medicare Initial Enrollment, or ACA Open Enrollment.

Note the exact start and end date for that window -- missing it can mean waiting up to a year.

If none of these windows apply to your situation, check whether a life event opened a Special Enrollment Period instead.

Call before the deadline if you want help comparing options before you decide.

Medicare Annual Enrollment Period (AEP): October 15 - December 7

Medicare's Annual Enrollment Period runs October 15 through December 7 every year -- the same dates nationwide. During this window you can switch between Original Medicare and Medicare Advantage, change Medicare Advantage plans, or join, switch, or drop a Part D prescription drug plan. Changes take effect January 1 of the following year.

October 15 - December 7, 2026 for coverage starting January 1, 2027
Open to anyone already on Medicare
Lets you switch Advantage plans, switch to/from Original Medicare, or change Part D coverage

Medicare Advantage Open Enrollment Period (MA OEP): January 1 - March 31

If you're already enrolled in a Medicare Advantage plan, you get one more chance early in the year to make a single change -- switch to a different Medicare Advantage plan, or drop Advantage and return to Original Medicare (and add a standalone Part D plan). This window is narrower than AEP: it's only for people already in a Medicare Advantage plan, and only allows one plan change.

January 1 - March 31 every year
Only for people already enrolled in Medicare Advantage
Allows one plan change, not unlimited switching

Medicare Initial Enrollment Period (IEP): a 7-month window around turning 65

Your first chance to sign up for Medicare is a 7-month window: the 3 months before your 65th birthday month, your birthday month itself, and the 3 months after. Missing this window can mean a permanent late-enrollment penalty on Part B, not just a delay.

ACA Marketplace Open Enrollment: November 1 - January 15

For 2027 Marketplace coverage, Open Enrollment runs November 1, 2026 through January 15, 2027 in most states -- some state-run exchanges set their own, sometimes longer, dates. Enroll or change plans by December 15 for coverage starting January 1; enroll between December 16 and January 15 and coverage starts February 1 instead.

November 1, 2026 - January 15, 2027 in most states
Enroll by December 15 for a January 1 start
Enroll December 16 - January 15 for a February 1 start
Some state-run exchanges use different dates -- confirm yours

Outside these windows: Special Enrollment Periods

Missed a window? A qualifying life event -- losing job-based coverage, losing Medicaid or CHIP, turning 26, marriage, or a new baby, among others -- can open a Special Enrollment Period outside the normal calendar. Use the Special Enrollment Period Eligibility Checker to see whether yours is likely still open.

Common questions about this topic

What's the difference between Medicare AEP and Medicare Advantage OEP?

AEP (Oct 15 - Dec 7) is open to everyone on Medicare and allows multiple types of changes. MA OEP (Jan 1 - Mar 31) is only for people already in a Medicare Advantage plan and allows just one change.

Do ACA Open Enrollment dates ever change by state?

Yes. November 1 - January 15 is the federal default that most states on HealthCare.gov use, but some state-run exchanges set their own, sometimes longer, enrollment windows -- confirm your specific state's dates before assuming the federal calendar applies.

I missed my enrollment window. What are my options?

Check whether a qualifying life event gives you a Special Enrollment Period -- job loss, losing Medicaid, turning 26, marriage, and having a baby are common ones. If nothing applies, you may need to wait for the next scheduled window, though a licensed agent can help confirm what's available now.

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