As of 2013, a Medicare surtax of 3.8 percent applies to taxpayers in higher income brackets, according to Forbes. The 3.8 percent surtax applies to earnings that exceed defined thresholds, Fidelity explains.
The Medicare surtax applies in two ways to higher-income earners, states Fidelity. First, those taxpayers pay the 3.8 percent surtax either on the amount by which their modified adjusted gross income exceeds a defined threshold or on their net investment income, whichever is less. Second, those taxpayers must pay an additional 0.9 percent tax on earnings that exceed the thresholds, bringing the Medicare payroll tax they pay on those earnings to a total of 3.8 percent.