Key Points Medicare enrollees have to pay a monthly premium for Part B. Higher earners can be subject to surcharges called IRMAAs. It's important to know how IRMAAs are calculated and how to avoid them. The $23,760 Social Security bonus most retirees completely overlook › One of the biggest misconceptions about Medicare is that coverage under it is free. While Medicare Part A, which covers hospital care, is generally free for enrollees, Part B, which covers outpatient care, charges a monthly prem ...