Current income tax provisions bear little resemblance to those enacted by the original law, the Revenue Act of 1913. Because of the progressive nature of the federal income tax, a need for special provisions for capital gains was recognized. In 1921, gains from the sale or disposition of capital assets and certain other capital items were identified and taxed differently from income from other sources. The capital gains provisions resulted in the separation of ordinary and capital gains income.

Gains and losses from the sale or exchange of a capital asset and other capital items are classified as either short- or long-term, depending on the period of time the property is held. Income from items held for less than the required period is taxed as ordinary income. Income from items held for longer than the required period receive preferential treatment only if the net long-term gain exceeds the net short-term capital loss. If long-term capital gains are realized, 60 percent of the excess gain is claimable as a deduction; the remaining 40 percent of the net gain is taxed at the taxpayer's ordinary tax rate. If the net short-term capital gain exceeds the net long-term loss, 100 percent of the excess is taxable at the normal rate.