Medicare Enrollment Periods: When You Can Sign Up and Switch
Medicare runs on a calendar. There are five enrollment periods, each with its own rules about who can act and what they can change — and missing the wrong one can mean penalties that last for life. This hub explains all five in plain English so you know exactly when your window is open.
The five enrollment periods at a glance
- Initial Enrollment Period (IEP) — the 7-month window around your 65th birthday when you first sign up for Medicare.
- Annual Enrollment Period (AEP) — October 15 to December 7, when anyone can join, switch, or drop a Medicare Advantage or Part D plan for the coming year.
- Medicare Advantage Open Enrollment Period (OEP) — January 1 to March 31, a one-time change for people already enrolled in a Medicare Advantage plan.
- Special Enrollment Periods (SEPs) — windows opened by qualifying life events such as moving or losing employer coverage.
- General Enrollment Period (GEP) — January 1 to March 31, a fallback for people who missed their IEP and do not qualify for an SEP.
Why the timing matters
Two of these periods protect you from penalties (the IEP and SEPs), and the others let you fine-tune your coverage each year. If you enroll late in Part B or Part D without creditable coverage, the penalties are permanent — so the calendar is not just bureaucracy, it is money. If you are approaching 65, start with the turning 65 guide and your enrollment timeline.
Explore each enrollment period
Your 7-month window around your 65th birthday to first sign up.
October 15 – December 7: change Advantage and Part D plans.
January 1 – March 31: a one-time switch if you are on Advantage.
Life events — moving, losing coverage — that open a window.
January 1 – March 31: a fallback if you missed your IEP.
Not sure which window applies to you right now? A licensed advisor can confirm your dates and make sure you do not miss a deadline — at no charge. You can also take our 2-minute Medicare quiz to see where you stand.
Frequently Asked Questions
What are the Medicare enrollment periods?
There are five: the Initial Enrollment Period (IEP) when you first turn 65, the Annual Enrollment Period (AEP, October 15 – December 7), the Medicare Advantage Open Enrollment Period (OEP, January 1 – March 31), Special Enrollment Periods (SEPs) triggered by life events, and the General Enrollment Period (GEP, January 1 – March 31) for people who missed their IEP.
What is the difference between AEP and the Medicare Advantage OEP?
During AEP (October 15 – December 7) anyone can join, switch, or drop a Medicare Advantage or Part D plan. The Medicare Advantage OEP (January 1 – March 31) is narrower: only people already in a Medicare Advantage plan can use it, and only to make one change.
What happens if I miss my Initial Enrollment Period?
If you do not have other creditable coverage, you may have to wait for the General Enrollment Period (January 1 – March 31) to sign up, and you can face lifelong late-enrollment penalties for Part B and Part D. 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. Original Medicare, Medicare Advantage, and Part D changes are tied to specific windows. The main exceptions are Special Enrollment Periods triggered by qualifying life events such as moving, losing other coverage, or qualifying for Extra Help.
Talk to a Licensed Medicare Advisor
Get a free, no-obligation review of your Medicare options from a licensed advisor.
Get My Free ReviewThis 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 2026-06-15 by Lynsey Brennan, Licensed Medicare Advisor (FL #G007269).