Medicare Timing & Deadlines
Medicare has six different enrollment periods, each with its own rules and deadlines. Missing the wrong one can mean a permanent penalty — here's exactly which one applies to you.
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Unlike most insurance, Medicare doesn’t have a single yearly sign-up window. Depending on your situation — turning 65, missing your original deadline, losing other coverage, or simply wanting to review your current plan — a different enrollment period applies, each with its own dates and rules. Using the wrong one, or missing your window entirely, can mean a permanent late-enrollment penalty added to your premium for life.
Below is every Medicare enrollment period explained in plain English, so you know exactly which one applies to you right now. If you’re brand new to Medicare and want the fundamentals first, start with our complete New to Medicare guide — this page assumes you already understand the basics and focuses specifically on timing and deadlines.
7 months around your 65th birthday. Your first chance to enroll.
January 1 – March 31 each year. For those who missed their IEP.
Triggered by a qualifying life event, like losing employer coverage.
October 15 – December 7 every year. Switch Advantage or Part D plans.
January 1 – March 31. One-time switch if you’re already in Medicare Advantage.
6 months, once in your life. Guaranteed-issue window for Supplement plans.
Your Initial Enrollment Period is a 7-month window: the 3 months before your 65th birthday month, your birthday month itself, and the 3 months after. This is your first opportunity to enroll in Medicare Part A and Part B.
Example: If your 65th birthday is in June, your IEP runs from March 1 through September 30. Enrolling in the 3 months before your birthday month means coverage typically starts the month you turn 65.
If you missed your Initial Enrollment Period and don’t qualify for a Special Enrollment Period, the General Enrollment Period runs every year from January 1 through March 31. Coverage begins the month after you enroll.
⚠ Important: Enrolling during GEP after missing your IEP without a qualifying exception can trigger a permanent late-enrollment penalty on your Part B premium — 10% for each 12-month period you were eligible but didn’t enroll.
A Special Enrollment Period lets you enroll outside the standard windows, without penalty, when triggered by a qualifying life event. The most common:
An 8-month SEP begins the month after your employment or group coverage ends, whichever comes first.
Moving out of your plan’s service area, or to an area with new plan options, can trigger an SEP.
Changes in Medicaid or Low-Income Subsidy eligibility can open a special window.
Every year from October 15 through December 7, anyone already enrolled in Medicare can switch Medicare Advantage plans, switch Part D prescription drug plans, or move between Original Medicare and Medicare Advantage. Changes take effect January 1 of the following year. This is the one enrollment period most current Medicare beneficiaries hear about every fall.
Every year from January 1 through March 31, if you’re already enrolled in a Medicare Advantage plan, you get one opportunity to make a single change — switch to a different Medicare Advantage plan, or drop Medicare Advantage entirely and return to Original Medicare (adding a Part D plan if needed). Unlike AEP, this period is only for people already in a Medicare Advantage plan, and only allows one change.
Your Medigap Open Enrollment Period is a one-time, 6-month window that begins the month you’re both 65 or older and enrolled in Medicare Part B. During this window, insurers must offer you any Medigap policy they sell at their best available rate — no health questions, no denial for pre-existing conditions.
⚠ This one matters most: Once this 6-month window closes, insurers in most states can require medical underwriting to approve you for a Medigap policy — or deny you outright. If a Medigap plan is part of your plan at all, this window is the one to protect above all others.
Which enrollment period applies to me right now?
It depends entirely on your situation — whether you’re newly turning 65, already enrolled and reviewing your options, or dealing with a life change like losing employer coverage. The fastest way to know for sure is a quick, free conversation with a licensed advisor.
Can I have more than one enrollment period apply to me at the same time?
Yes — for example, you could be in your Medigap Open Enrollment Period while also being eligible for AEP if you’re deciding between Original Medicare with a Supplement plan versus Medicare Advantage.
What happens if I miss all of my enrollment windows?
You’ll typically need to wait for the next General Enrollment Period (January 1 – March 31), and may face permanent late-enrollment penalties on your Part B and/or Part D premiums, depending on how long you went without coverage.
Is there a cost to get help figuring out my enrollment window?
No. Our consultations are always free, with no obligation. We’re compensated by the insurance carrier when you enroll, at no additional cost to you.
Now that you know your timing, visit the Medicare hub to explore every plan type, region, and topic — or head back to the full New to Medicare guide for the complete picture.
We encourage you to review these official government resources as part of your Medicare decision.
⚠ Medicare Disclaimer: This information is for educational purposes only and is not a complete description of enrollment rules. Rules and deadlines may change. Contact a licensed Medicare agent for guidance specific to your situation. NISONA is an independent insurance agency and is not affiliated with Medicare or the Social Security Administration.
No pressure. No obligation. We’ll help you figure out exactly which window applies to your situation — and make sure you don’t miss it.
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