January 1 to March 31
General Enrollment Period
If you didn’t sign up for Part A (if you have to buy it) and/or Part B (for which you must pay premiums) during your Initial Enrollment Period, and you don’t qualify for a Special Enrollment Period, you can sign up between January 1–March 31 each year. Your coverage won’t start until July 1 of that year, and you may have to pay a higher Part A and/or Part B premium for late enrollment. If you enroll in Parts A and B during this period, you have three months (April through June) to enroll in a Part D plan or to enroll in a Medicare Advantage plan. Enrolling in Medigap plans depends on state laws.