Medicare has five enrollment windows, and people mix them up constantly. Each one lets you do different things. Here they are in the order you will meet them.
Initial Enrollment Period (IEP)
Seven months around your 65th birthday: three before, the birthday month, three after. Enroll in Part A, Part B, Part D, or a Medicare Advantage plan. Miss it and you wait for the General Enrollment Period and may owe a penalty.
Medigap Open Enrollment
Six months starting the month you are 65 or older and enrolled in Part B. Any Medicare Supplement sold in your state must accept you at the standard rate regardless of health. After it closes, most states allow carriers to ask health questions. This is the window people regret missing most.
Annual Enrollment Period (AEP)
October 15 to December 7 every year. Switch between Original Medicare and Advantage, change Advantage plans, add, drop, or change a Part D plan. Changes take effect January 1.
Medicare Advantage Open Enrollment (MA OEP)
January 1 to March 31. Only for people already in a Medicare Advantage plan. One change: switch to a different Advantage plan, or drop back to Original Medicare and pick up a Part D plan. You cannot use it to go from Original Medicare into Advantage.
General Enrollment Period (GEP)
January 1 to March 31 for people who missed their IEP and have no Special Enrollment Period. Coverage begins the month after you enroll. Late penalties may apply.
Special Enrollment Periods (SEP)
- Leaving employer coverage after 65: eight months to enroll in Part B without penalty, but only two months to join an Advantage or Part D plan.
- Moving out of your plan's service area.
- Your plan leaves the market or loses its contract.
- Qualifying for Extra Help or Medicaid, which allows changes throughout the year.
- A 5-star plan in your area can be joined once per year at any time.
This guide is general information, not advice about a specific policy. Benefits, enrollment rules, and costs vary by state, carrier, and year. Confirm details for your situation with a licensed agent.
