401(k) and FICA
According to the IRS, FICA withholdings consist of two distinct taxes: a Social Security tax and a Medicare tax. 401(k) contributions are not exempt from FICA withholdings. For example, if you make $42,000 in a year and contribute $3,000 to a 401(k), you pay federal income taxes on only $39,000. However, you must still pay FICA withholdings based on your full income of $42,000.