Definition
The Additional Medicare Tax is an extra 0.9% applied to wages above certain income thresholds: $200,000 for single filers and head of household, and $250,000 for married filing jointly. It was created by the Affordable Care Act.
Your employer is required to withhold the additional 0.9% once your wages from that employer exceed $200,000 in a calendar year — regardless of your filing status or your spouse's income. This means that if you and your spouse each earn $180,000, no additional Medicare tax is withheld during the year, but you'll owe 0.9% on $110,000 ($360,000 combined − $250,000 threshold) when you file.
If you're in this situation, you can use Step 4c to add extra withholding to cover the anticipated liability.
How this affects your W-4
If you expect to owe Additional Medicare Tax because your combined household income exceeds the MFJ threshold, use Step 4c to add extra withholding each paycheck. Calculate the shortfall and divide by your remaining pay periods.
The calculator displays the Additional Medicare Tax separately in the take-home breakdown when applicable.
See how additional medicare tax affects your withholding
Use the free W-4 calculator to calculate your exact withholding with your specific situation.
Open the W-4 Calculator →Related terms
Medicare Tax
The 1.45% payroll tax withheld from all wages to fund Medicare — no wage cap.
FICA
The combined Social Security and Medicare payroll taxes — 7.65% of wages for most employees.
Step 4c — Extra Withholding
A line on the W-4 where you specify a flat dollar amount to withhold from every paycheck in addition to the calculated amount.