The employer tax is measured by the amount of wages paid after 1954 with respect to employment after 1936. See Sec. 31.3121(a)-1, relating to wages, and Secs. 31.3121(b)-1 to 31.3121(b)-4, inclusive, relating to employment. For provisions relating to time of payment of wages, see Sec. 31.3121(a)-2. [T.D. 6744, 29 FR 8306, July 2, 1964]