income tax , levy imposed on individuals (or family units) and corporations. Individual income tax is computed on the basis of income received. It is usually classified as a direct tax because the burden is presumably on the individuals who pay it. Corporate income tax is imposed on net profits, computed as the excess of receipts over allowable costs.
As an instrument of national policy, the individual income tax has played different roles in different countries at different times, beginning in Great Britain at the close of the 18th century. By 1914 the “personal” income tax had come to be regarded in a number of countries not only as an important revenue instrument but also as an instrument for achieving social reform through income redistribution. Finally, in most countries it has been used to redirect economic decisions through preferential treatment of various activities. It can also act as a stabilizer against economic fluctuations because its effect on purchasing power varies inversely with changes in income and employment. For example, a person who experiences a reduction of income due to a job loss will typically owe less in taxes; the employed person will pay more in taxes but will have more income available for purchases. More recently, however, opinion has shifted away from the view that the income tax should be used for these purposes because of the costs involved, in terms of disincentives and other distortions of economic behaviour.
Regarding income taxes on corporations, nearly all countries assess them, but the provisions and rates differ widely. Since industrialized countries generally have larger corporate sectors than less-developed countries, corporation income taxes in developed countries tend to be greater in relation to national income and total government revenue—except in major mineral-producing areas of less-developed countries.
The United Kingdom for a long time applied the income tax on corporations (companies) purely as a supplement to the taxation of individuals. Shareholders had to pay tax on dividend income only to the extent that the rate of individual tax applicable to such income exceeded the corporate rate; they received refunds if that rate was less than the corporate rate. This system was modified in 1937 and replaced in 1965 by a separate corporation tax.