When you sign up for a Part D plan, your coverage start date depends on which enrollment period you use. During the Annual Enrollment Period from October 15th through December 7th, your Part D coverage becomes effective January 1st of the following year. If you enroll during your Initial Enrollment Period when turning 65, coverage starts the first day of your birthday month. For example, if you turn 65 on September 8th and enroll in August, your Part D plan becomes effective September 1st. If you delayed Medicare enrollment while working with employer coverage, your Part D coverage begins the first day of the month following your enrollment. The Medicare Advantage Open Enrollment Period from January 1st through March 31st only allows changes to existing Medicare Advantage plans or switching back to Original Medicare, but cannot be used for initial Part D enrollment. Special Enrollment Periods may also apply in qualifying circumstances, with coverage typically starting the month after enrollment depending on your specific situation.
