The Revenue Act of 1942 (also called "the Victory Tax of 1942 ")

In 1939 only about five percent of American workers paid income tax. The United States' entrance into World War II changed that figure. The demands of war production put almost every American back to work, but the expense of the war still exceeded tax-generated revenue. President Roosevelt's proposed Revenue Act of 1942 introduced the broadest and most progressive tax in American history, the Victory Tax. Now, about 75 percent of American workers would pay income taxes. Because so many citizens paid the tax, it was considered a mass tax. To ease workers' burden of paying a large sum once a year, and to create a regular flow of revenue into the U.S. Treasury, the government required employers to withhold money from employees' paychecks. Additional taxes were put in place in 1943. By war's end in 1945, about 90 percent of American workers submitted income tax forms, and 60 percent paid taxes on their income. The federal government covered more than half its expenses with new income tax revenue

Information from "Understanding Taxes". The Internal Revenue Service.  [Online] Available at  http://www.irs.gov/app/understandingTaxes/jsp/whys/lp/IWT2L5lp.jsp