An alternative trading system (ATS) is a non-exchange trading venue approved by regulatory authorities like the Securities and Exchange Commission (SEC) and Financial Services Authority (FSA). In the broadest sense, an ATS is an alternative venue - usually an electronic system - where buyers and sellers can execute trades in existing financial instruments. Instruments may include shares, bonds and derivatives. An ATS provides an additional pool of liquidity to trade in existing instruments. No new securities can be listed on an ATS.