Income tax in the United States These treaties reduce the chance of double taxation by allowing each country to fully tax its citizens and residents and reducing the amount the other country can tax them. Generally the treaties provide for reduced rates of tax on investment income and limits as to which business income can be taxed. The treaties each define which taxpayers can benefit from the treaty. The United States social insurance system is funded by a tax similar to an income tax. Social Security tax of 6.2% is imposed on wages paid to employees. The tax is imposed on both the employer and the
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