An Act amending the act of August 24, 1961 (P. L. 1135, No. 508), entitled "An act imposing a tax for general public school purposes in school districts of the first class A on salaries, wages, commissions and other compensation earned by residents thereof, and on the net profits earned from businesses, professions or other activities conducted by residents thereof; ***," further providing for the withholding by employers of taxes and increasing the interest and penalties assessed for late payments.