Initial Coverage Election Period (ICEP)
You can enroll when you first become eligible for Medicare (three months before the month you turn age 65 until three months after the month you turn age 65). If you get Medicare due to a disability, you can join from three months before to three months after your 25th month of cash disability payments.

November 15 - December 31 (Annual Election Period)
If you are eligible for Medicare, you can enroll in or switch plans during the Annual Election Period. For example, you can switch from Original Medicare to a Medicare Advantage Plan (like a HIP VIP Medicare Plan). Your coverage will be effective on January 1 of the upcoming year.

January 1 - March 31 (Open Enrollment Period)
If you are already enrolled in a Medicare plan, you can switch plans once during the Open Enrollment Period, but you cannot add or drop Medicare prescription drug coverage. For example, you can switch from Original Medicare and a Prescription Drug Plan (PDP) to a Medicare Advantage Plan with prescription drug coverage (MA-PD).

After March 31
You generally cannot make any other changes to your Medicare coverage for the remainder of the year unless you meet special exceptions, such as if you move, if you have Medicaid coverage, or if you get extra help in paying for your drugs.