Which dark pools were fined, and for what: Barclays, Credit Suisse, UBS and ITG?

Several of the biggest dark pools were fined between 2015 and 2016, and the common thread was not that dark pools are illegal but that some operators told clients one thing and did another. These were settlements: the firms agreed to pay without a trial, and only some admitted wrongdoing.

The headline cases came on 31 January 2016, when the US Securities and Exchange Commission and the New York Attorney General announced settlements with Barclays and Credit Suisse. Barclays admitted wrongdoing and paid $35 million to each, $70 million in total. Credit Suisse paid $30 million to each plus $24.3 million in disgorgement and interest, $84.3 million in total, without admitting or denying the findings.

What had they done? On Barclays, the SEC said the bank sold clients on a tool called Liquidity Profiling, which would police its LX dark pool for predatory trading, yet did not continuously police it, did not run the weekly surveillance reports it described, and sometimes overrode the tool by moving subscribers to less aggressive categories. On Credit Suisse, it said the firm accepted over 117 million illegal sub-penny orders in its Crossfinder pool and failed to treat subscribers' order information confidentially.

Two other cases fit the pattern. In January 2015 UBS agreed to pay $14.4 million over violations the SEC said ran from 2008 to 2012. In August 2015 ITG and its affiliate settled for $20.3 million over operating a secret trading desk and misusing subscribers' confidential information. SEC Chair Mary Jo White said the agency would continue to "shed light on dark pools".