a tax levied on profits in excess of a stipulated standard of “normal” income. There are two principles governing the determination of excess profits. One, known as the war-profits principle, is designed to recapture wartime increases in income over normal peacetime profits of the taxpayer. The other, identified as the high-profits principle, is based on income in excess of some statutory rate of return on invested capital.

The modern excess-profits tax was first instituted during World War I as a revenue measure and an instrument of curbing excess profits attributable to the war. Excess-profits taxes were levied during World War II and the Korean War (1950–53) in most of the countries whose business earnings were affected by the war. Excess-profits taxes based on the high-profits principle have become part of the peacetime tax structure of a few countries such as Denmark and several South American countries.

The economic effects of an excess-profits tax are usually reckoned in terms of two basic criteria: (1) their efficacy in siphoning off wartime “windfalls” in order to bring about a stabilizing effect on the economy; (2) their effect on economic incentives, production levels, and business expenditure. The integration of an excess-profits tax within the total tax structure of a country, particularly in relation to existing corporation taxes and individual income taxes, and the determination of what is “excess” also pose serious problems.