Customers banking with Santandar and HSBC are in line for a refund after failing to alert customers when they went into their overdraft, a watchdog has said.
The Competition and Market Authority said the bank broke rules by not sending messages allowing people to avoid unarranged overdraft charges.
HSBC said it would refund a total of £8m to 115,000 customers.
Santander also said it would comply, although it's yet to work our the cost as yet.
The CMA said the banks first breached the rules in February 2018, when, it's been revealed, that if customers went into an unarranged overdraft between 10.45pm and 11.45pm, when balances were calculated, they were not alerted by text.
Most were told the next day, after fees had already been charged.
An HSBC spokesman said they are contacting customers who incurred overdraft charges as a result of these issues to apologise and provide a refund.
A Santander spokesperson said: “We have carried out a detailed review to understand why the errors happened and have taken steps to fix the issues. We are now working to identify and refund all affected customers as quickly as possible.”