26 USC 3301 - Rate of tax

There is hereby imposed on every employer (as defined in section 3306 (a)) for each calendar year an excise tax, with respect to having individuals in his employ, equal to
(1) 6.2 percent in the case of calendar years 1988 through 2008; or
(2) 6.0 percent in the case of calendar year 2009 and each calendar year thereafter;

of the total wages (as defined in section 3306 (b)) paid by him during the calendar year with respect to employment (as defined in section 3306 (c)).