Energy supplier Ovo has been fined £8.9million by industry regulator Ofgem for overcharging customers and sending out inaccurate and incomplete information.
The business, which is headquartered in Bristol, sent out inaccurate annual statements to more than 500,000 customers, according to the ruling.
The issues were caused by IT problems and also included some customers being undercharged and many not receiving an annual statement.
The problems took place between 2015 and 2018, and Ovo says it has since put measures in place, such as investments in technology and implementing appropriate compliance procedures, to make sure the same errors do not happen again.
Ovo Energy did not self-report the majority of the issues and was slow to put things right, according to Ofgem which claims the energy supplier was aware of the problems.
The company has since refunded the customers affected by overcharging and has also written off all amounts owing from customers who had been charged at the wrong rates.
The business has agreed to pay the £8.9million fine into a voluntary fund to help vulnerable customers.
Anthony Pygram, director of conduct and enforcement at Ofgem, said: “Ovo Energy billed a number of its customers incorrectly and issued them with inaccurate information.
“The supplier did not prioritise putting these issues right whilst its business was expanding.
“Our enforcement action sends a strong message that suppliers must get basic services right for all their customers. Ovo Energy has accepted the breaches and put processes in place to comply with the rules in future.”
Ovo said in a statement: "Since the day we were founded, serving our customers has been our number one priority. We strive to give them the best experience by working hard to provide the latest digital innovations and excellent service.
"We have pioneered a new business model for the industry and have constantly innovated to simplify energy for our customers.
"OVO Energy holds itself to high standards, but we have not always got it right. We accept Ofgem’s findings of issues regarding estimation processes, information formatting and pricing errors.
"We are proud of our record. In particular, during the time these infringements occurred, we were voted Uswitch Supplier of the Year four out of five times and achieved a customer satisfaction score of 96 per cent - the highest in the survey’s 11 year history at the time.
"We will continue to be guided by the current and future needs of our customers and will keep innovating towards a zero carbon world."
The news comes just weeks after Ovo sealed a massive deal with a rival supplier which will mean millions of people are switched over to them.
