The "Tobin tax" is a proposed tax on speculative currency transactions. It was named after the late Nobel Prize-winning economist James Tobin, who suggested the idea in 1972 to reduce volatility and speculation in the foreign-exchange markets. Advocates of the tax see it as a way to discourage excessive risk-taking and share the wealth of big banks.
Tobin said it had to to be an internationally agreed uniform tax to work effectively. He suggested each government would levy it with the proceeds paid into a global financial body such as the World Bank or the International Monetary Fund (IMF). However, it proved difficult to get global agreement on the tax.
The Harkin-DeFazio tax would levy a 25-basis-point (0.25%) fee on stock transactions over $100,000 and a two- or three-basis-point charge on derivatives transactions, including futures, options and swaps, including credit-default swaps. Bloomberg News reported the proposed trading tax was supported by more than 200 economists, the AFL-CIO, and business leaders including Warren Buffett and Vanguard founder John Bogle.
France introduced a financial transaction tax on August 1, 2012. In addition, Belgium, Finland, Ireland, Italy, Poland, Switzerland and the UK currently levy financial transaction taxes, but taxation differs significantly across countries. 
For example, Switzerland levies a 0.15-0.30 percent stamp duty on the transfer of equities and bonds involving a Swiss securities dealer, while France's financial transaction tax that taxes equity trades at 0.3 percent and high-frequency-trading at 0.01 percent.
The European Union had proposed an EU-wide financial transaction tax in 2011 that would have levied a 0.1 percent tax on the transfer of shares and bonds and a 0.01 percent tax on derivative contracts. However, negotiations came to a halt after resistance from several EU member states, and an EU-wide policy was not adopted.
In July 2020, the financial transaction tax again came into focus when European leaders agreed to create a 750-billion-euro ($858 billion) recovery fund to rebuild EU economies hit by the coronavirus crisis. To fund the plan, the EU gave their blessing “in principle” to new EU-wide taxation powers to shore up Brussels’s finances, including a tax on financial transactions, as well as on digital services, carbon and plastic. 
- Trading Tax -- a Bad Idea Whose Time Has Come. Barron's.
- Leading American economists back campaign for "Tobin Tax". The Guardian.
- It's time for a 'Tobin tax' on financial transactions. The Economic Times.
- French Financial Transaction Tax Overview. London Stock Exchange.
- Financial Transaction Taxes in Europe. Tax Foundation.
- EU leaders strike'historic'$2 trillion deal to rebuild Europe's economy. CNN Business.