The costs of settling a number of class-action lawsuits and slower-than-expected business in its tax and mortgage arms caused H&R Block Inc.’s third-quarter profits to drop 68 percent and forced the company to lower annual revenue estimates, the nation’s largest tax preparer said Thursday.

H&R Block also said it would restate earnings for fiscal years 2005 and 2004, as well as the first two quarters of the year, to correct accounting errors it said led to the company understating its income tax liability last year by $32 million.

For the three months ending Jan. 31, the Kansas City, Mo.-based company reported earnings of $28.9 million, or 9 cents per share, compared with $92.3 million, or 28 cents per share, during the same period a year ago. Analysts surveyed by Thomson Financial had expected earnings of 26 cents per share.