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Medicare Enrollment Periods: Don’t Miss Your Window

Medicare runs on a strict calendar, and the wrong miss can cost you for life. Whether you are signing up at 65, switching plans in the fall, or reacting to a life event, this guide points you to the exact enrollment period that applies — and the deadline that protects you.

What are the Medicare enrollment periods and when are they?

There are five: the Initial Enrollment Period (the 7 months around your 65th birthday), the Annual Enrollment Period (October 15 – December 7), the Medicare Advantage Open Enrollment Period (January 1 – March 31), Special Enrollment Periods (triggered by life events), and the General Enrollment Period (January 1 – March 31) for those who missed their IEP.

  • Sign up during your Initial Enrollment Period to avoid lifelong Part B and Part D penalties.
  • Use the Annual Enrollment Period each fall to review and change Advantage or Part D plans.
  • Special Enrollment Periods open after qualifying events such as moving or losing employer coverage.

Key Takeaways

  • Your Initial Enrollment Period is a 7-month window around your 65th birthday.
  • The Annual Enrollment Period (Oct 15 – Dec 7) is when anyone can change Advantage or Part D coverage.
  • The Medicare Advantage Open Enrollment Period (Jan 1 – Mar 31) is only for people already in an Advantage plan.
  • Late enrollment without creditable coverage causes permanent Part B and Part D penalties.

Your enrollment timeline

The deadlines that matter, in order.

  1. 1

    3 months before 65

    Your Initial Enrollment Period opens — enroll early so coverage starts on time.

  2. 2

    Around your 65th birthday

    Take premium-free Part A; enroll in Part B unless you have creditable employer coverage.

  3. 3

    Oct 15 – Dec 7 (yearly)

    Annual Enrollment Period — review and change Medicare Advantage or Part D plans.

  4. 4

    Jan 1 – Mar 31 (yearly)

    Medicare Advantage Open Enrollment, plus the General Enrollment Period for missed sign-ups.

  5. 5

    After a qualifying life event

    A Special Enrollment Period may open — act within your specific deadline.

The costly mistakes to avoid

Where people in this situation lose the most money.

Missing the Initial Enrollment Period

People who assume Medicare is automatic can miss their 7-month window, get stuck waiting for the General Enrollment Period, and pay a lifelong Part B penalty.

Confusing AEP with the Medicare Advantage OEP

The fall Annual Enrollment Period is open to everyone; the spring Open Enrollment Period only lets current Advantage members make one change. Mixing them up means a missed opportunity.

Not knowing a life event opened a window

Moving or losing employer coverage opens a Special Enrollment Period with its own deadline. Miss it and you may face penalties or a wait until the next general window.

Guides, tools & resources

Frequently Asked Questions

What happens if I miss my Initial Enrollment Period?

Without other creditable coverage, you may have to wait for the General Enrollment Period (January 1 – March 31) to sign up, and you can owe permanent Part B and Part D late-enrollment penalties. A Special Enrollment Period may apply if you delayed because you had employer coverage.

Can I change my Medicare plan any time of year?

Generally no. Changes are tied to specific windows — mainly the Annual Enrollment Period and, for current Advantage members, the Open Enrollment Period. The exception is a Special Enrollment Period triggered by a qualifying life event.

What is the difference between AEP and the Medicare Advantage OEP?

AEP (October 15 – December 7) is open to everyone and allows multiple changes. The Medicare Advantage OEP (January 1 – March 31) is only for people already in a Medicare Advantage plan and allows one change.

Talk to a Licensed Medicare Advisor

Get a free, no-obligation review of your Medicare options from a licensed advisor who works your situation, not a sales script.

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This information is for educational purposes only and is not legal, tax, or insurance advice. Medicare rules, premiums, and income thresholds change annually — confirm current figures with Medicare.gov, the Social Security Administration, or a licensed advisor. HealthPlan Connect is not affiliated with or endorsed by the federal Medicare program or any government agency. Last reviewed 2026-06-12 by Lynsey Brennan, Licensed Medicare Advisor (FL License #G007269).

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