Annual Enrollment Period (AEP)
October 15 – December 7
The Annual Enrollment Period is the primary window for Medicare beneficiaries to make plan changes. During AEP you can switch from Original Medicare to a Medicare Advantage plan, change Advantage plans, join or switch Part D prescription drug plans, or drop coverage and return to Original Medicare. All changes take effect January 1 of the following year.
- Join, switch, or drop a Medicare Advantage plan
- Join or switch a standalone Part D plan
- Return to Original Medicare from Advantage
- Changes take effect January 1
Medicare Open Enrollment Period (OEP)
January 1 – March 31
The Medicare Open Enrollment Period gives beneficiaries already in a Medicare Advantage plan one opportunity to make a change. You can switch to a different Advantage plan or disenroll and return to Original Medicare with a standalone Part D drug plan. You cannot use this period to enroll in Medicare Advantage for the first time or to switch standalone Part D plans if you are on Original Medicare.
- Switch to a different Medicare Advantage plan
- Drop Medicare Advantage and return to Original Medicare
- Pick up a Part D plan when returning to Original Medicare
- One plan change allowed during this period
Initial Enrollment Period (IEP)
Seven-month window around your 65th birthday
Your Initial Enrollment Period begins three months before the month you turn 65, includes your birthday month, and continues for three months after. This is when you first enroll in Medicare Parts A and B. Enrolling on time is important — delaying Part B enrollment without qualifying coverage can trigger permanent premium penalties.
- Starts 3 months before your 65th birthday month
- Includes your birthday month
- Ends 3 months after your birthday month
- Enroll in Part A, Part B, and optionally Part D or Advantage
Special Enrollment Periods (SEPs)
Special Enrollment Periods allow you to make Medicare plan changes outside standard enrollment windows when you experience qualifying life events. These events give you a limited time — typically two months — to enroll in or change plans without waiting for AEP.
Common qualifying events
- Moving to a new area outside your plan's service region
- Losing employer or union group health coverage
- Qualifying for Medicaid or Extra Help (LIS)
- Your plan leaves Medicare or reduces its service area
- Moving into or out of a skilled nursing facility
- Experiencing a natural disaster or other emergency
Late Enrollment Penalties
Medicare charges ongoing premium penalties if you delay enrollment without qualifying coverage. These penalties are added to your monthly premiums for as long as you have Medicare, making timely enrollment critical.
Part B late penalty
Your Part B premium increases by 10% for each full 12-month period you were eligible but did not sign up. For example, if you waited 24 months past your IEP, you would pay a 20% surcharge on your Part B premium permanently.
Part D late penalty
The Part D penalty is 1% of the national base beneficiary premium multiplied by the number of full months you went without creditable drug coverage. This amount is recalculated each year and added to your monthly Part D or Advantage plan premium.
Key Dates at a Glance
- Oct 15 – Dec 7: Annual Enrollment Period (AEP) — make plan changes for next year
- Jan 1 – Mar 31: Open Enrollment Period (OEP) — switch or drop Advantage plans
- 3 months before to 3 months after turning 65: Initial Enrollment Period (IEP)
- Varies: Special Enrollment Periods triggered by qualifying life events