If an individual already has Medicare Part A, and he wishes to sign up for Part B, he completes form CMS 40-B and mails or delivers it to his local Social Security Office, says the Social Security Administration. Enrollment is within a seven-month time frame of the applicant's 65th birthday.
Eligibility for Medicare begins at the age of 65. Individuals can sign up during the seven-month period that starts three months before they turns 65, during the month of their 65th birthday, and three months after they turns 65, according to the Social Security Administration. If an individual does not sign up during that specific time frame, he can enroll between Jan. 1 and March 31 each year.
If the applicant did not sign up during his seven-month eligibility period, and he did not sign up during the general enrollment period, he can sign up during a special enrollment period. The applicant needs to be covered under a group health plan from his current employer any time he or his spouse is working. There is also an eight-month enrollment period that starts the month after the applicant's employment ends or his group health plan ends, says the Social Security Administration.