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Part D enrollment periods explained

When you can enroll in, switch, or drop a Part D plan — and the key dates you need to know.

Initial Enrollment Period (IEP)

Your IEP is a 7-month window when you first become eligible for Medicare. For most people, this is around their 65th birthday:

  • Starts: 3 months before your 65th birthday month
  • Includes: Your birthday month
  • Ends: 3 months after your birthday month

This is the most important enrollment window. Missing it without creditable coverage triggers the permanent late enrollment penalty.

Annual Election Period (AEP)

October 15 – December 7 each year. During this time, any Medicare beneficiary can:

  • Join a Part D plan
  • Switch from one Part D plan to another
  • Drop Part D coverage

Coverage changes made during AEP take effect on January 1 of the following year.

Open Enrollment Period (OEP)

January 1 – March 31 each year. If you're in a Medicare Advantage plan, you can:

  • Switch to a different Medicare Advantage plan (with or without drug coverage)
  • Drop your Medicare Advantage plan and return to Original Medicare (and enroll in a standalone Part D plan)

Note: This period does not allow switching between standalone Part D plans.

Special Enrollment Periods (SEPs)

Certain qualifying events let you make changes outside the regular windows. Common triggers include:

  • Moving out of your plan's service area
  • Losing employer or union drug coverage
  • Gaining or losing Medicaid eligibility
  • Entering or leaving a nursing home
  • Your plan leaving Medicare or reducing its service area

If you receive Extra Help, you have a continuous Special Enrollment Period that allows you to change plans once per calendar quarter (January through September).