Medicare AEP vs. OEP

Christian Worstell
In this article...
  • AEP is the Medicare Annual Enrollment Period, while OEP can refer to one of several Medicare Open Enrollment periods. Learn how to avoid potential penalties or loss of coverage by picking the right Medicare OEP you need for the type of Medicare plan you want.

Medicare has several different enrollment periods, each with their own acronym. And one instance that creates a lot of confusion is Medicare AEP vs. OEP.

Mixing up the acronyms for the various enrollment periods may lead you to mix up the time at which you can enroll or switch your Medicare coverage. Missing an enrollment period can have consequences such as late enrollment penalties and lapses in coverage.

In this review, we detail Medicare AEP vs. Medicare OEP to help clear up the confusion and make sure you sign up for the right Medicare plan at the appropriate time. 

What Is the Medicare Annual Enrollment Period (AEP)?

AEP stands for “Annual Enrollment Period.” Sometimes you may also see referred to as “Annual Election Period.” 

This enrollment period lasts from October 15 to December 7 every year. Anyone who is currently enrolled in Medicare is eligible to participate.

Many incoming and current Medicare beneficiaries use the terms “Medicare open enrollment period” or “fall Medicare open enrollment period” when talking about AEP. That’s because AEP is by nature an enrollment period that is “open” to all Medicare beneficiaries.

But the term “open enrollment period” may also apply to two other enrollment periods that are separate and different from AEP.

What Can You Do In AEP?

Here are all the things you can do during AEP:

  1. Enroll in a Medicare Advantage (Medicare Part C) plan
  2. Enroll in a Medicare Part D, or PDP plan
  3. Switch your Medicare Advantage plan to another
  4. Change from one Medicare Part D plan to another
  5. Drop your Medicare Advantage plan and switch back to Original Medicare (Medicare Parts A and B)
  6. Drop your Medicare Part D plan

Any changes you make during AEP will take effect on January 1 of the upcoming year. 

How Many Changes Can I Make During AEP?

You can make as many changes as you want during AEP. The final change that you make will be the one that becomes final.

For example, you might enroll in one Medicare Advantage plan during AEP but then decide to switch to another Medicare Advantage plan before the end of AEP. The plan you switch to by the end of AEP would be the plan that will go into effect for you Jan. 1 of the following year.

What Is Medicare Open Enrollment (OEP)? 

OEP stands for “Open Enrollment Period.” There are several enrollment periods that this term may apply to. 

  • As detailed above, many beneficiaries refer to the Medicare Annual Enrollment Period (AEP) as the fall Medicare Open Enrollment Period. Both names apply to the enrollment period explained above that lasts from Oct. 15 to Dec. 7 every year.

  • The Medicare Advantage Open Enrollment Period is a different enrollment period. It takes place from January 1 to March 31 each year and is only open to those who are currently enrolled in a Medicare Advantage plan.

    During this time, you may switch from your current Medicare Advantage plan to a different one or drop the plan and switch back to Original Medicare. This is true even if the plan you’re dropping or switching from is one you signed up for in the most recent Medicare AEP.

  • The Medicare Supplement Open Enrollment Period is another different enrollment period, and it applies only to Medicare Supplement Insurance (also called Medigap).

    Your Medigap Open Enrollment Period begins the day you are at least 65 years old and enrolled in both Medicare Part A and Part B, and it only lasts for six months. If you want to enroll in a Medicare Supplement plan to help pay for your Medicare Part A and Part B costs such as copays, coinsurance, deductibles and more, your Medigap OEP is your best time to sign up for a plan.

    You can technically enroll in a Medigap plan at any time throughout the year. But doing so during your Medigap Open Enrollment Period protects you from medical underwriting, which is when insurance companies ask health questions or require you to undergo a physical exam and then base your premiums or eligibility on the status of your health. 

    During your six-month Medigap OEP, insurance companies can’t use medical underwriting. Your best chance to get a Medicare Supplement plan with rates that aren’t based on your health is to enroll when you have guaranteed issue rights, such as during your Medigap OEP.

If you’re preparing to enroll in Medicare or have questions about Medicare enrollment, be sure to learn more about the type of Medicare coverage you’re interested in so that you can prepare an time your enrollment decisions correctly.

How Many Changes Can I Make During An OEP? 

During AEP and the Medigap Open Enrollment Period, you can make an unlimited number of changes. 

But during the Medicare Advantage Open Enrollment Period from Jan. 1 to March 31 each year, you are granted only one change. That means once you change your coverage during this time, there is no going back, and you must keep your new plan until your next opportunity to make Medicare enrollment changes. 

What Other Medicare Enrollment Periods Are There?

AEP, Medigap OEP and Medicare Advantage OEP are just three Medicare enrollment periods. For more information about other Medicare enrollment periods, visit our Medicare Eligibility and Enrollment Guide

If you’re ready to compare Medicare Advantage plans and consider enrollment, or if you’re simply gathering free plan quotes to compare your options before Medicare Open Enrollment, you can request a free plan quote or call to speak with a licensed insurance agent who can help answer your questions.

Christian Worstell
About the Author

Christian Worstell is a senior Medicare and health insurance writer with He is also a licensed health insurance agent. Christian is well-known in the insurance industry for the thousands of educational articles he’s written, helping Americans better understand their health insurance and Medicare coverage.

Christian’s work as a Medicare expert has appeared in several top-tier and trade news outlets including Forbes, MarketWatch, WebMD and Yahoo! Finance.

While at HelpAdvisor, Christian has written hundreds of articles that teach Medicare beneficiaries the best practices for navigating Medicare. His articles are read by thousands of older Americans each month. By better understanding their health care coverage, readers may hopefully learn how to limit their out-of-pocket Medicare spending and access quality medical care.

Christian’s passion for his role stems from his desire to make a difference in the senior community. He strongly believes that the more beneficiaries know about their Medicare coverage, the better their overall health and wellness is as a result.

A current resident of Raleigh, Christian is a graduate of Shippensburg University with a bachelor’s degree in journalism. You can find Christian’s most recent articles in our blog.

If you’re a member of the media looking to connect with Christian, please don’t hesitate to email our public relations team at

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