Tobin tax

A Tobin tax, suggested by Nobel Memorial Prize in Economic Sciences Laureate economist James Tobin, was originally defined as a tax on all spot conversions of one currency into another. Tobin's original tax was intended to put a penalty on short-term financial round-trip excursions into another currency. By the late 1990s, however, the term Tobin tax was being incorrectly used to describe all forms of short term transaction taxation, whether across currencies or not - another term for these broader tax schemes is Robin Hood tax due to tax revenues from the (presumably richer) speculator funding general revenue (of whom the primary beneficiaries are poorer). More exact terms however apply to different scopes of tax.

One non-tax regulatory equivalent of Tobin's (very narrow original) tax is to require "non-interest bearing deposit requirements on all open foreign exchange positions.". If these deposit requirements result in forfeits or losses if a currency suddenly declines due to speculation, they act as inhibitions against deliberate speculative shorts of a currency. However, they would not raise funds for other purposes, so are not a tax.

Tobin suggested his currency transaction tax in 1972 in his Janeway Lectures at Princeton, shortly after the Bretton Woods system of monetary management ended in 1971. Prior to 1971, one of the chief features of the Bretton Woods system was an obligation for each country to adopt a monetary policy that maintained the exchange rate of its currency within a fixed value—plus or minus one percent—in terms of gold. Then, on August 15, 1971, United States President Richard Nixon announced that the United States dollar would no longer be convertible to gold, effectively ending the system. This action created the situation whereby the U.S. dollar became the sole backing of currencies and a reserve currency for the member states of the Bretton Woods system, leading the system to collapse in the face of increasing financial strain in that same year. In that context, Tobin suggested a new system for international currency stability, and proposed that such a system include an international charge on foreign-exchange transactions.

...
Wikipedia