The tax for any calendar year is measured by the amount of wages paid by the employer during such year with respect to employment after December 31, 1938. (See Sec. 31.3306(b)-1, relating to wages, and Secs. 31.3306(c)-1 to 31.3306(c)-3, inclusive, relating to employment.) [T.D. 6658, 28 FR 6632, June 27, 1963]