When you may enroll & when coverage begins

Medicare advantage plans

In most cases, your coverage becomes effective on the first day of the next month after you join. However, if you enroll in a 2017 plan between October 15 and December 7, your coverage will become effective January 1.

Prescription drug plans

In most cases, your coverage becomes effective on the first day of the next month after you join. However, if you enroll in a 2017 plan between October 15 and December 7, your coverage will become effective January 1. If you purchase a stand-alone prescription drug plan while you're enrolled in a Medicare Advantage plan with prescription drug coverage, you will be disenrolled automatically from your Medicare Advantage plan.

Medicare Supplement insurance plans

In most cases, your coverage becomes effective on the first day of the next month after you join—unless you request a different effective date. Your Medicare Supplement Open Enrollment Period continues for six months after you sign up for Medicare Part B or upon your 65th birthday. During this time a company must allow you to buy any Medicare Supplement plan offered in your state.