determined under state law, and often is based on federal taxable income. Most states conform to many federal concepts and definitions, including defining income and business deductions and timing thereof. State rules vary widely regarding to individual itemized deductions. Most states do not allow a deduction for state income taxes for individuals or corporations, and impose tax on certain types of income exempt at the federal level. Some states have alternative measures of taxable income, or alternative taxes, especially for corporations. States imposing an income tax generally tax all income of corporations organized in the state and individuals residing in the state. Taxpayers from another state are subject to tax only on income earned in the state or apportioned to the state. Businesses are subject to income tax in a state only if they have sufficient nexus in (connection to) the state. Non-residents Foreign individuals and corporations not resident in the United States are subject to federal income tax only on income from a U.S. business and certain types of income from U.S. sources. States tax individuals resident outside the state and corporations organized outside the state only on wages or business income within the state. Payers of some types of income to non-residents must withhold federal or state income tax on the payment. Federal withholding of 30% on such income may be reduced under a tax treaty. Such treaties do not apply to state taxes. Alternative tax bases (AMT, states) An alternative minimum tax (AMT) is imposed at the federal level on a somewhat modified version of taxable income. The tax applies to individuals and corporations. The tax base is adjusted gross income reduced by a fixed deduction that varies by taxpayer filing status. Itemized deductions of individuals are limited to home mortgage interest, charitable contributions, and a portion of medical expenses. AMT is imposed at a rate of 26% or 28% for individuals and 20% for corporations, less the amount of regular tax. A credit against future regular income tax is allowed for such excess, with certain restrictions. Many states impose minimum income taxes on corporations or a tax computed on an alternative tax base. These include taxes based on the capital of corporations and alternative measures of income for individuals. Details vary widely by state. Differences between book and taxable income for businesses In the United States, taxable income is computed under rules that differ materially from