<P> Federal social insurance taxes are imposed on employers and employees , ordinarily consisting of a tax of 12.4 % of wages up to an annual wage maximum ( $118,500 in wages , for a maximum contribution of $14,694 in 2016 ) for Social Security and a tax of 2.9 % ( half imposed on employer and half withheld from the employee 's pay ) of all wages for Medicare . The Social Security tax is divided into 6.2 % that is visible to employees ( the `` employee contribution '' ) and 6.2 % that is visible only to employers ( the `` employers contribution '' ) . For the years 2011 and 2012 , the employee 's contribution had been temporarily reduced to 4.2 % , while the employer 's portion remained at 6.2 % , but Congress allowed the rate to return to 6.2 % for the individual in 2013 . To the extent an employee 's portion of the 6.2 % tax exceeded the maximum by reason of multiple employers , the employee is entitled to a refundable tax credit upon filing an income tax return for the year . </P>
what percentage of gross income is withheld as an employee 's contribution to social security
12.4 % of wages up to an annual wage maximum