Group expects full year combined operating ratio of 95%.
RSA has reported a 9% rise in its first-half operating profit.
The group posted an operating result of £440m, up from £403m a year ago.
Profit after tax was up 23% to £292m in the six months to 30 June 2008, from £237m in the same period last year.
The insurer also posted net written premiums of £3.4bn, up 12% from £2.9bn at this stage in 2007.
Its combined operating ratio was 93%. In a statement, RSA said it now expected to deliver a combined operating ratio for the full year of better than 95%.
Andy Haste, Group CEO of RSA, said: "It has been another good first half and we have once again delivered strong results in what are challenging trading and economic conditions. These results continue to demonstrate the positive impact of our management actions and the benefit of the Group's strong and diversified portfolio.
"With these actions and the strength of the portfolio, we remain confident in the Group's ability to continue to deliver sustainable profitable performance. As it stands today, we now expect to achieve a combined operating ratio for 2008 of better than 95%. The outlook for the Group is positive, and this is reflected in the 10% increase in the interim dividend to 2.73p (H1 2007: 2.48p)."