An investigation into past stock option grants at Apple has found that chief executive Steve Jobs was aware of procedural irregularities but did not benefit personally from the grants or understand the accounting implications.

Apple revealed the results of the investigation in documents filed with the US Securities and Exchange Commission (SEC) today.

The company also said it was restating its financial results with a total impact of $84m, including $21m combined for the years 2004, 2005 and 2006 as a result of the options probe.

The investigators found that Apple made a number of stock grants where the grant dates were intentionally selected to obtain favourable exercise prices. They reported serious concerns over the way that two former officers, whom Apple did not name, accounted for stock option grants.

Jobs appeared to have been exonerated by the investigation, however. "The board of directors ... has complete confidence in Steve Jobs and the senior management team," Apple said in its statement.