Enrollment Windows: IEP, AEP, and MA OEP Defined
Initial Enrollment Period (IEP)
Your Initial Enrollment Period is your seven-month window around your 65th birthday to first sign up for Medicare.
It spans three months before your birthday month, your birth month, and three months after. Enrolling on time protects you from lifelong late enrollment penalties.
If you continue working past 65 with qualifying employer group coverage, you may delay Part B without penalty until you retire.
Annual Enrollment Period (AEP)
The Annual Enrollment Period runs every fall from October 15 through December 7. Changes made during this 2026 window take effect on January 1, 2027.
During AEP, you can switch Medicare Advantage plans, return to Original Medicare, or choose a new Part D drug plan.
Comparing your prescription drug list on Medicare.gov every autumn ensures your preferred pharmacy and medications remain covered at reasonable rates.
Review your plan’s Annual Notice of Change every September to see how your copays, premiums, and drug formularies will shift for the coming year.
Medicare Advantage Open Enrollment Period (MA OEP)
The Medicare Advantage Open Enrollment Period runs annually from January 1 through March 31. This window is only for individuals already enrolled in Medicare Advantage.
You can switch to another Advantage plan or return to Original Medicare. You cannot use it to join Medicare Advantage for the first time.
If you switch back to Original Medicare during MA OEP, you also have the right to purchase a stand-alone Part D drug plan.
Where to Find Unbiased Guidance
Use the official Medicare Plan Finder on Medicare.gov to compare your local plan choices side by side.
For free, objective counseling from trained volunteers, contact your local State Health Insurance Assistance Program (SHIP).
You can also call official Medicare representatives at 1-800-MEDICARE (1-800-633-4227) for help at any time.
