When you first become eligible for Medicare which is often when you turn 65 — 3 months before or after your 65th birthday or initial Medicare eligibility.

If you are currently on Medicare — Between October 15 and December 7 for a January 1 effective date.

Anytime under special circumstances, such as if you move out of your plan’s service area or if you lose your group coverage.

The Medicare Advantage Open Enrollment Period (MA OEP) is the time when you can switch from one Medicare Advantage Plan to another, or switch from a Medicare Advantage Plan to Original Medicare with or without a Part D plan. The MA OEP occurs each year from January 1 through March 31, and changes take effect on the first of the month following the month you enroll. You can only make one change during the MA OEP.

The best time to buy a Medigap policy is during your Medigap Open Enrollment Period. This is the 6-month period that starts the first day of the month you're 65 or older and signed up for Part B. After this period, your options to buy a Medigap policy may be limited and the policy may cost more. Often, carriers allow applications to be submitted up to 90 days prior to Medicare eligibility date.