You can apply three months before you turn 65, the month you turn 65, and three months after you turn 65. This is called your Initial Enrollment Period (IEP). You can enroll for Part B coverage up to eight months after you stop working. This small period of time is called Part B Special Enrollment Period (SEP).If you are eligible for Part B but you do not enroll during the eight-month period, you may face a late enrollment fee. If you do not take advantage of the SEP or IEP, you can enroll anytime during January 1 through March 31 of each year. This is called the General Enrollment Period. Your coverage will start on July first. You are automatically enrolled in Medicare once you have been collecting SS for 24 months or you turn 65.