Medicare

Annual Enrollment Period (AEP)

The AEP is the primary annual opportunity for Medicare beneficiaries to change their Medicare Advantage or Part D drug plan, with changes taking effect January 1.

Last reviewed: May 2026 · Editorial methodology

Definition

The Annual Enrollment Period (AEP), also called the Fall Open Enrollment Period, runs October 15 through December 7 each year and is the primary window during which Medicare beneficiaries can make changes to their Medicare Advantage and Part D coverage. During AEP, beneficiaries may switch from one Medicare Advantage plan to another, switch from Medicare Advantage back to Original Medicare (with or without adding a stand-alone Part D plan), switch between stand-alone Part D plans, or add Part D coverage for the first time (though a late enrollment penalty may apply if they went without creditable coverage). All AEP elections take effect January 1 of the following year. AEP is distinct from the Medicare Advantage Open Enrollment Period (MA OEP), which runs January 1–March 31 and allows beneficiaries already enrolled in MA to make one plan change. It is also distinct from Special Enrollment Periods triggered by qualifying events. Beneficiaries should compare plans annually during AEP because formularies, premiums, networks, and extra benefits change year to year.

Where this term matters

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Tip

Glossary definitions are educational. Always check your own policy language — insurers can define common terms differently from one another. When in doubt, request a written explanation from your agent.

Related terms

Medicare Part C (Medicare Advantage)Medicare Advantage plans deliver all Original Medicare benefits through private insurers and frequently include prescription drug coverage, dental, vision, and hearing benefits.Medicare Part DMedicare Part D covers prescription drugs and features a $2,100 out-of-pocket cap in 2026, ending the coverage gap that previously left beneficiaries with full costs.Initial Enrollment Period (IEP)Your IEP spans three months before, the month of, and three months after your 65th birthday — missing it can result in permanent late enrollment penalties.Medicare Special Enrollment PeriodA Medicare SEP lets you enroll in Medicare without late penalties when you lose qualifying employer coverage or experience other defined life events.Open Enrollment PeriodOpen enrollment is your primary annual opportunity to choose or update health coverage; missing it typically means waiting another year without a qualifying life event.

Related guides

Source: Cover Forge USA editorial team|Last verified: May 2026|Methodology
Definitions are educational and may be simplified. Always refer to your policy contract and consult a licensed agent for terms that affect coverage decisions.
CF

Cover Forge USA Editorial Team

Editorial Lead

This article was researched and written by the Cover Forge USA editorial team against federal sources (NAIC, CMS, FEMA, DOL, SSA, state DOIs) and standard policy forms. Bylines organize content by topic — they do not assert individual licensure. See our editorial-policy for details.

Reviewed June 2026

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