The announcement was meant to sooth investor fears the investigation might blow up into a bigger accounting scandal.
Tosh said that it was likely to mark down operating profit for the three years ended March 2014 by $420 million.
Shares had fallen 13 percent since Toshiba spooked investors on May 8, saying it was extending an investigation into inappropriate reporting of some infrastructure project costs and construction work.
The reason investors were spooked was because this would be Toshiba’s second accounting investigation in less than two years.
The company is in the process of setting up a third-party committee to investigate irregularities, which Toshiba said could reach a different conclusion on treatment of markdowns. The widening of an investigation first announced in April had prompted Toshiba to delay its quarterly earnings announcement and cancel a year-end dividend.
As a result of the extended probe, Toshiba said it would not be able to announce financial results for the latest fiscal year until June or later. The firm would normally have released earnings by early May.