RBS, which is 81-percent owned by the government after a vast bailout amid the global financial crisis, took a £1.455 billion accounting charge on changes to the value of its debt in the third quarter.
The Edinburgh-based lender also took another £400 million hit to compensate clients who were mis-sold insurance. That took its total bill for the insurance mis-selling scandal to £1.7 billion.
RBS added that the cost of an IT meltdown in June had risen by £50 million to a total of £175 million.
At the same time, the bank sold another £7.0 billion of non-core assets, while impairment losses were cut to £1.176 billion in the reporting period.
"Having made strong progress, RBS targets most of the restructuring actions from its 2009 strategic plan to be substantially completed in the next 15-18 months," an RBS statement said.
Turning to its role in the Libor rate-rigging affair, RBS warned that it would likely face financial penalties from the scandal which has already wreaked havoc at rival British bank Barclays.