The employee's Social Security tax rate for 2015 is 6.2% of the first $118,500 of wages, salaries, etc. An employee's 2015 earnings that are in excess of $118,500 are not subject to the Social Security tax.

The Social Security tax is one component of what is known as the FICA payroll tax. The other component is the Medicare tax, which applies to every dollar of an employee's earnings. In other words, there is no wage limit or cap for the Medicare tax.

In addition to the employee's Social Security tax, there is also an employer's Social Security tax.