SVB Holdings expects to lose an estimated £20m as a result of the terrorist attacks in the US, it announced.
The sum is equivalent to just over 10p a share before tax.
The firm, which operates within Lloyd's, said it expected its syndicate 1007 to lose £8m, 1212 to lose £7m, 1241 to lose £4m and syndicates 575 and 2147 to lose £8m.
The estimates include reinsurance payments but exclude profits from other trading.
The costs will be included in company results for the second half of this year.
