Payday lender CFO Lending has agreed to fork out £34 million to redress 97,000 customers who it had overcharged, taken unauthorised payments from and sent threatening letters to.
The Financial Conduct Authority (FCA) said that the settlement consists of £31.9 million written-off customers' outstanding balances and £2.9 million in cash payments.
The FCA's director of supervision Jonathan Davidson said: "We discovered that CFO Lending was treating its customers unfairly and we made sure that they immediately stopped their unfair practices.
"Since then we have worked closely with CFO Lending, and are now satisfied with their progress and the way that they have addressed their previous mistakes."
The financial watchdog's charge sheet against CFO Lending also included "routinely" reporting inaccurate information about customers to credit reference agencies and showing incorrect loan balances for customers, so that some ended up repaying more money than they owed.