Paddy Power Betfair has been fined £2.2 million by the UK's gambling watchdog, for failing to protect customers who were displaying signs of problem gambling.
The Gambling Commission also says the company failed to stop stolen money being gambled.
It says "significant amounts" of stolen money flowed through the exchange, and Paddy Power Betfair has a duty to "prevent the proceeds of crime from being used in gambling."
The Gambling Commission's revealed one punter was able to gamble away large sums of cash stolen from a charity.
The company, which has its headquarters in Dublin, admits it breached its social responsibility and are focusing on making sure it doesn't happen again.