The parent company to CNA, Loews Corp, said it would restate three years of results to change accounting for reinsurance contracts.
CNA said it would restate 2002 to 2004 results to change its accounting for several reinsurance contracts with former affiliate Accord Re, and its former equity interest in Accord.
The restatement will reduce Loews' net worth as of 31 December 2004, by $27.3m and CNA's net worth by $29m.
According to reports the changes will increase 2002 and 2004 profits, and reduce 2003 losses, for both companies.
CNA said it was responding to subpoenas and other regulatory requests from New York attorney general Eliot Spitzer and was examining several companies' reinsurance practices.
CNA profit totalled $178m, compared with a year-earlier loss of $124m.
Revenue for the commercial insurer fell 13% to $2.38bn as increased competition caused property and casualty net written premiums to decline, Leows said.