Another large financial institution has been caught gouging customers.

Raymond James Financial Services agreed to settle allegations Tuesday with six state securities regulators for charging unreasonable commissions on trades that harmed investors. The broker-dealer will pay at least $8.2 million in refunds to clients, and $4.2 million in penalties and costs.

A task force of state regulators from Alabama, California, Illinois, Massachusetts, Montana, and Washington investigated Raymond James’s compensation practices, and found that it charged excessive commissions on more than 270,000 low-principal amount equity transactions nationwide in the last five years.

Raymond James took a commission on these transactions of more than 5 percent, sometimes taking 100 percent of the proceeds from a customer’s sale. It overcharged customers by applying a $75 minimum commission charge, regardless of the reasonableness of the commission. Over the past five years, Raymond James took more than $8,250,000 in excess commissions from investors.

“Regardless of how large or small an investor’s transactions may be, the people and companies making these transactions on behalf of investors have a duty to ensure adherence to the law,” William Beatty, director of the Division of Securities for the Washington State Department of Financial Institutions, said.

This isn’t the first time Raymond James has overcharged customers, said William Galvin, secretary of the Commonwealth of Massachusetts.

“In 2011, they paid more than $2 million in restitution and fines for conduct that was identical to this,” Galvin said.

The Tuesday settlement also requires the broker-dealer to change its supervisory and compliance procedures on brokerage commissions.

The lesson? Question everything when you work with a big corporation.