RBS will take a £300m (€382m) hit for an IT meltdown this summer, which left millions of people unable to access their money and for its role in mis-selling PPI.
IT problems at the group inconvenienced thousands of Irish Ulster Bank customers in particular.
RBS is expected to say in its half-year results that it is increasing the compensation pot for those who bought payment protection insurance by about £130m (€165m).
Following last month's computer glitch, it is setting aside £125m (€159m) to compensate customers and improve IT systems.
But RBS boss Stephen Hester said: “We have continued to make the bank safer and stronger as we clean up problems of the past.”