Legal history of income tax in the United States Legal history of income tax in the United States Taxation of income in the United States has been practised since colonial times. Some southern states imposed their own taxes on income from property, both before and after Independence. The Constitution empowered the federal government to raise taxes at a uniform rate throughout the nation, and required that "direct taxes" be imposed only in proportion to the Census population of each state. Federal income tax was first introduced under the Revenue Act of 1861 to help pay for the Civil War. It was renewed in later years and reformed in 1894
Income tax in the United States insurance (Social Security) taxes in 2016. The table below also does not reflect changes, effective with 2013 law, which increased the average tax paid by the top 1% to the highest levels since 1979, at an effective rate of 33%, while most other taxpayers have remained near the lowest levels since 1979. Income tax is imposed as a tax rate times taxable income. Taxable income is defined as gross income less allowable deductions. Taxable income as determined for federal tax purposes may be modified for state tax purposes. The Internal Revenue Code states that "gross income means all income from