1918-1919 The Revenue Act of 1918, actually passed in early 1919, made relatively few major changes in the tax structure, but it did raise rates on individual and corporate income, corporate excess profits, and estates. The law provided for normal and surtax rates that rose the dizzying
level of 77 percent on the biggest incomes. Corporations were given an exemption of $2,000, but rates were raised to 12 percent on net taxable income. The law also rectified numerous mistakes in earlier revenue laws, most of which had been enacted in great haste.
The income tax now occupied a central place in the federal revenue system. In 1916, income taxes had been providing 16 percent of federal revenue. From 1917 to 1920, that percentage ranged as high as 58 percent. The tax was now a pillar of federal finance. Still, however, it remained a narrow levy. In 1920, only 5.5. million returns showed any tax due.
May 27: Wilson makes his famous "politics is adjourned" speech to urge higher taxes, including levies on income, estates, and excess profits.
Meanwhile, the BIR began a massive recruitment campaign to help redress its chronic personnel shortage. More than 1,000 auditors were hired in the first six months of 1919. The agency still struggled to keep up, however; delays in the printing of tax forms and instructions prompted an extension of the filing deadline from March 1 to April 1.
William G. McAdoo, Wilson's Secretary of the Treasury. Photo courtesy of National Archives.
October 27: Volstead Act, providing for enforcement of the new Prohibition Amendment, passed over Wilson's veto. BIR commissioner was charged with enforcing the act. A new Prohibition Unit was created on December 22, allowed a budget of 2 million under the Volstead Act.
You're probably right that few paid though.