The United Kingdom’s financial market watchdog, the Financial Conduct Authority (FCA Financial Conduct Authority (FCA) The Financial Conduct Authority (FCA) is the largest financial regulator for all financial markets in the United Kingdom (UK).The UK regulator is responsible for the conduct of firms authorized under the Financial Services and Markets Act 2000. Moreover, the FCA is also responsible for the regulation of behavior in retail and wholesale financial markets, supervision of the trading infrastructure that supports those markets, and the prudential regulation of firms not regulated by the PRA.