Form 8959, Part III: Additional Medicare Tax, is used to report and calculate the Additional Medicare Tax for individuals with wages, compensation, or self-employment income in excess of certain thresholds. Forms 1040, 1040-SR, 1040-NR, and 1040-SS are the U.S. Individual Income Tax Return forms. When filing these forms, you may need to complete and attach Form 8959 if you are subject to the Additional Medicare Tax. Form 8959 provides the necessary space to calculate and report the tax.