After hammering the financial services industry the past three years with billions of dollars in penalties for failing to retain written communications, federal regulators are reminding firms to keep a sharp watch on their audio messaging.

In September, the Commodity Futures Trading Commission charged the Minnesota-based brokerage firm CHS Hedging with failing to make or retain 3,000 audio recordings during transactions with clients. Minnesota-based CHS cooperated with the probe and settled it by agreeing to pay a $650,000 penalty. A company spokesperson said CHS is committed to improving its compliance and risk management practices.