Medicare Glossary

Annual Enrollment Period (AEP)

The period each year from October 15 through December 7 when Medicare beneficiaries can change their Medicare Advantage or Part D drug plans. Changes take effect January 1 of the following year.

Also known as: Fall Open Enrollment

COBRA Continuation Coverage

A federal law allowing you to temporarily keep employer group health coverage after leaving a job, usually at your own full cost. COBRA is not considered creditable coverage for delaying Medicare enrollment, so missing your Medicare window while on COBRA can trigger a penalty.

Also known as: COBRA

Creditable Coverage

Health or prescription drug coverage that is at least as good as Medicare's standard coverage. If you have creditable coverage when you turn 65, you may be able to delay enrolling in Medicare without facing a late enrollment penalty.

Disenrollment

The process of leaving a Medicare Advantage or Part D plan. You can only disenroll during specific enrollment periods, such as the Annual Enrollment Period or a Special Enrollment Period. When you disenroll from a Medicare Advantage plan, you return to Original Medicare.

Employer Group Health Plan (EGHP)

Health coverage offered through an employer, either your own or a spouse's, that may let you delay Medicare enrollment without a late penalty if the coverage is creditable and the employer has 20 or more employees.

Also known as: EGHP, Group Health Plan

Initial Enrollment Period (IEP)

The 7-month window around your 65th birthday during which you can first sign up for Medicare. It includes the 3 months before your birthday month, your birthday month, and the 3 months after. Enrolling during the first 3 months gets you the earliest coverage start.

Also known as: IEP

Late Enrollment Penalty

A higher premium added permanently to your Part B or Part D premium if you don't sign up for coverage when you are first eligible and don't have other qualifying coverage. The Part B penalty is 10% for each full 12-month period you were eligible but didn't enroll. The Part D penalty is 1% of the national base premium per month.

Also known as: LEP

Open Enrollment Period (OEP)

For Medicare Advantage, the period from January 1–March 31 each year when enrolled MA beneficiaries can switch to a different MA plan or return to Original Medicare (with Part D if desired). Changes take effect the first of the following month.

Also known as: OEP, Medicare Advantage OEP

Special Enrollment Period (SEP)

A window outside the standard enrollment periods during which you can join, switch, or drop a Medicare plan. SEPs are triggered by qualifying life events such as losing employer coverage, moving, gaining Medicaid eligibility, or your plan leaving the area.

Also known as: SEP

ZIP Code Enrollment

The process of using your ZIP code to find Medicare Advantage or Part D plans available in your area. Plan availability, provider networks, and premiums can vary significantly based on your geographic location.