After the initial enrollment period for Part B expires, sign up occurs during one of these times:
General Enrollment Period —January 1–March 31 each year; coverage will begin on July 1. There may be a late enrollment penalty.
Special Enrollment Period
—If an individual or their spouse is working and covered by a group health plan based on that work, or disabled, they may choose to wait to sign up for Part B. For working seniors, sign up for Part B can take place anytime if there is group health plan coverage based on current employment or during the 8-month period that begins the month after the employment ends, or the group health plan coverage ends, whichever happens first. Even with COBRA coverage, enrollment in Part B without penalty must be done during the 8‑month period that begins the month after the employment ends.
If there is a delay signing up for Part B, it only becomes available during the general enrollment period, and there may be a significant late enrollment penalty. The monthly premium for Part B may go up 10% for each full 12-month period that an individual was eligible, but did not enroll. Usually, there is no a late enrollment penalty if sign up for Part B takes place during a special enrollment period.