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Medicare Enrollment Timeline
Key dates every Medicare beneficiary should know — from turning 65 through Annual Enrollment Period and Special Enrollment Periods.
Last updated Jul 11, 2026
3 months before birthday month
Initial Enrollment Period (IEP) opens
Your 7-month IEP begins. This is the primary window to enroll in Part B and choose supplemental coverage without late penalties.
- •Mark your exact IEP dates on the calendar
- •Gather provider and prescription lists
- •Research Advantage vs. Medigap paths for your county
Birthday month
Coverage can start this month
If you enrolled in the three months before your birthday month, Part B coverage typically begins the first day of your birthday month.
- •Confirm Part A and Part B effective dates
- •Complete Medigap or Advantage enrollment before IEP ends
3 months after birthday month
IEP closes
Missing Part B or Part D enrollment during IEP can trigger permanent late-enrollment penalties.
- •Finalize Part D enrollment if not bundled in Advantage
- •Save all enrollment confirmation documents
April – September
Medicare Advantage Open Enrollment (MA OEP)
If you are already in a Medicare Advantage plan, you may have a one-time switch opportunity early in the year (Jan 1 – Mar 31). Rules vary — confirm eligibility.
- •Review whether your current Advantage plan still fits
- •Compare one switch option if dissatisfied with current plan
September 30
Annual Notice of Change (ANOC) deadline
Plans must mail your ANOC by this date, outlining every change for the upcoming plan year.
- •Read your ANOC — do not discard it
- •Note network, formulary, and benefit changes
October 15 – December 7
Annual Enrollment Period (AEP)
The main window to switch Medicare Advantage or Part D plans. Changes take effect January 1.
- •Compare plans in your county before December 7
- •Verify doctors and prescriptions against new plan options
- •Enroll before the deadline — no extensions
Year-round
Special Enrollment Periods (SEPs)
Qualifying life events — moving, losing employer coverage, Medicaid changes — may open a limited enrollment window outside AEP.
- •Report address changes to Social Security and your plan
- •Act quickly — SEP windows are short and event-specific
Related resources
Prefer to Research on Your Own?
You can compare every plan available in your area and get unbiased, free help from official government resources:
Medicare Plan Availability: We do not offer every plan available in your area. Any information we provide is limited to those plans we do offer. Please contact Medicare.gov or 1-800-MEDICARE for all options. SwitchBlue Insurance Agency LLC is a licensed independent insurance agency and is not connected with or endorsed by the United States government or the federal Medicare program.