W-4 Withholding Instructions
There is a limit on the amount of wages that are taxed for Social Security, but there is no limit on wages that are taxed for Medicare.
Social Security Taxes
Your employer must withhold 6.2% of your income for old age, survivor, and disability insurance (OASDI), up to a maximum income of $142,800 (for 2021). Maximum income is defined as gross earnings less flexible spending and employee medical plan payroll deductions. The income ceiling generally rises each year.
For hospital insurance under Medicare, your employer must withhold 1.45% of gross earnings less flexible spending and employer medical plan payroll deductions, without any income limit.
Beginning January 1, 2013, an employer must withhold Additional Medicare Tax (0.9%) from wages it pays to an individual in excess of $200,000 in a calendar year, without regard to the individual’s filing status or wages paid by another employer.