For plan year 2023, the Late Enrollment Premium Penalty is $0.33 for each month that you were not enrolled in a Medicare Part D plan, but were eligible for Medicare Part D.
For our example, let’s say you had Part D coverage starting when you were initially eligible through 2010 and then decided that you did not need coverage starting January 1, 2012 so you dropped your Medicare Part D coverage. Your situation changed at the end of 2012 and you chose to enroll in a Part D plan for 2013, your monthly premium penalty would be $3.93 or 12 x $0.33.
Your Part D plan premium would be the regular plan premium plus an additional $3.93 each month.