The U.S. income tax system imposes a tax based on income on individuals, corporations, estates, and trusts. The tax is taxable income, as defined, times a specified tax rate. This tax may be reduced by credits, some of which may be refunded if they exceed the tax calculated. Taxable income may differ from income for other purposes (such as for financial reporting). The definition of taxable income for federal purposes is used by many, but far from all states. Income and deductions are recognized under tax rules, and there are variations within the rules among the states. Book and tax income may differ. Income is divided into "capital gains", which are taxed at a lower rate and only when the taxpayer chooses to "realize" them, and "ordinary income", which is taxed at higher rates and on an annual basis. Because of this distinction, capital is taxed much more lightly than labor.