As a result of the Affordable Care Act (ACA), the Additional Medicare Tax was added in 2013. Additional Medicare Tax rates are 0.9 percent and apply to highly compensated workers.
Individuals are liable for Additional Medicare Tax if their wages, compensation, or self-employment income (together with their spouse’s income if filing a joint return) exceed the threshold amount for their filing status.
You may have to make estimated tax payments if you anticipate that you will be liable for Additional Medicare Tax but will not be able to satisfy the liability through Additional Medicare Tax withholding.
In 2013, the Additional Medicare Tax went into effect and applied to wages, compensation, and self-employment income over a threshold amount received in taxable years after December 31, 2012.