26 U.S.C. § 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 6 percent of the total wages (as defined in section 3306(b)) paid by such employer during the calendar year with respect to employment (as defined in section 3306(c)). The amendments made by subsections (a) and (b) [amending this section, sections 3306 and 6157 of this title, and sections 1101 and 1105 of Title 42, The Public Health and Welfare] shall apply to remuneration paid after December 31, 1982 . The amendments made by subsection (c) [amending this section, sections 3302 and 6157 of this title, and section 1101 of Title 42 ] shall apply to remuneration paid after December 31, 1984 .”