Income tax in the United States increase complexity, irrespective of the system's flatness or lack thereof. Income tax is also levied by most U.S. states and many localities on individuals, corporations, estates, and trusts. These taxes are in addition to federal income tax and are deductible for federal tax purposes. State and local income tax rates vary from 1% to 16% of taxable income. Some state and local income tax rates are flat (single rate) and some are graduated. State and local definitions of what income is taxable vary highly. Some states incorporate the federal definitions by reference. Taxable income is defined separately and differently for
Working Tax Credit significant levels of overpayments. In order to reduce the overpayment problem, the income disregard was raised tenfold from £2,500 to £25,000 with effect from 2006/07. Income for tax credit purposes is "in principle" assessed similarly to UK income tax. Thus 'income' (c/f 'taxable income') consists of what the individual receives from gross earned and unearned sources—less allowances for 'expenditures' that would reduce that income. But, unlike income tax, tax credits measure income based on family 'household', rather than the individuals within. Also the effect of "income disregard" —to mask large annual increases in resources from reassessment— weakens comparisons with a