((a)) ** Tier 1 tax** In addition to other taxes, there is hereby imposed on every employer an excise tax, with respect to having individuals in his employ, equal to the applicable percentage of compensation paid during any calendar year by such employer for services rendered to such employer. For purposes of the preceding sentence, the term “applicable percentage” means the percentage equal to the sum of the rates of tax in effect under subsections (a) and (b) of section 3111 for the calendar year.

((b)) ** Tier 2 tax** In addition to other taxes, there is hereby imposed on every employer an excise tax, with respect to having individuals in his employ, equal to the percentage determined under section 3241 for any calendar year of the compensation paid during such calendar year by such employer for services rendered to such employer.

((c)) ** Cross reference** For application of different contribution bases with respect to the taxes imposed by subsections (a) and (b), see section 3231(e)(2).