A change to a system used to set foreign exchange rates resulted in incorrect prices being applied to some international transactions between March 2010 and May 2014.

This meant around 730,000 RBS and NatWest customers were charged an extra 60p for every £1,000 transacted. In total, around £40m is due to be refunded.

Once RBS had discovered the issue, it took steps to correct the system and then reviewed its data to identify all impacted transactions.

The refunds, including 8% statutory interest, are expected to be completed by Q3 2020. They will be automatic but if any customers believe they’re impacted, they should contact the bank.

An RBS spokesperson, said: “We are proactively refunding the difference, with interest, for incorrect foreign exchange rates that were applied to some international payments for certain customers between 2010 and 2014.

“We identified and addressed the source of the incorrect exchange rates in 2014, and put in place additional checks and controls to prevent this happening again. We apologise to those customers impacted.”