Income tax is a direct tax which is levied on the income of private individuals. Various income tax systems exist. Those range from a flat tax to an extensive progressive tax system.
Taxes levied on the income of companies is called corporate tax or corporation tax.
In order to help pay for its war effort in the American Civil War, the United States government issued its first income tax on August 5, 1861 as part of the Revenue Act of 1861 (3% of all incomes over US $800; rescinded in 1872).