tax levied on gains realized from the sale or exchange of capital assets (capital and interest). Capital gains have been taxed in the United States since the advent of federal income taxation. Since 1921 certain capital gains have been afforded preferential treatment.

Several arguments are used to support preferential treatment of capital gains. One is that encouraging the investment of risk capital stimulates economic growth. A second is that to tax in a single year the full value of several years' appreciation is unfair. A third is that taxing capital gains at the regular rates would tend to lock investors into their current patterns of investment. On the other hand, it is argued that preferential treatment results in distorted patterns of investment because regular income is converted into capital gains in order to avoid paying tax.

From an economic point of view, the crux of the issue of capital gains taxation is whether or not capital gains are part of ordinary income. If one defines income as the sum of the change in the individual's consumption and the change in his net worth, then capital gains should logically be taxed as ordinary income. If the definition of income operative in the British tax system (United Kingdom) is accepted, capital gains will not be taxed because they do not represent a continuing source of income.

In Great Britain until 1962, capital gains were not taxable and capital losses were not deductible. In 1962 speculative short-term (six months or less) gains were made taxable at the regular rates. In the United States, long-term (18 months or more) capital gains are subject to a maximum rate of 20 percent.