Health Insurance Center
Health Insurance Q & As
Meanwhile, there are only a couple instances in which you can change coverage between April and mid-November, the period known as the "off-season": (1) when you make a qualified change in your circumstances, for example moving out of the area covered by your health plan (called the "Special Enrollment Period" or SEP), and (2) when you first enroll in Medicare Parts A & B (the "Initial Enrollment Period" or IEP).
Finally, remember that the last six weeks of every year (November 15-December 31) is the "Annual Coordinated Election Period." Between these dates you can change plans as often as you want, with the final change taking effect January 1.