The correct answer is A. March 31. The General Enrollment Period (GEP) for Medicare Part B is the annual period for people who did not enroll when first eligible and who do not qualify for a Special Enrollment Period. According to the Centers for Medicare & Medicaid Services, the GEP runs each year from January 1 through March 31 . Medicare.gov and Social Security materials confirm the same timeframe for late enrollment into Part B.

This means the enrollment period ends on March 31 , making choices B, C, and D incorrect. May 31 and June 30 are outside the authorized general enrollment window, and December 31 is not the closing date for Part B’s GEP. Current CMS guidance also explains that when a person enrolls in Part B during the GEP, coverage begins the month after enrollment , rather than being delayed until July as under older rules. That timing update does not change the end date of the enrollment period itself, which remains March 31 . Therefore, under Medicare enrollment rules relevant to Accident and Health insurance licensing, the general enrollment period for Medicare Part B ends on March 31