IBM's accounting practices have been questioned by Wall Street analysts after it was discovered that the sale of a $340m (£237m) optical business unit was not mentioned in its recent results.
IBM shares fell $5 on Friday following a report in the New York Times which said that such transactions would normally be included in extraordinary items within a firm's balance sheet.
However, IBM had failed to do this and offset the transaction against operating costs to help it meet its earnings forecasts.
An IBM spokeswoman said the company had done nothing wrong, and had been quite open about the omission.
Chief executive Louis Gerstner had mentioned the transaction during the company's conference call to discuss fourth quarter results and had been accounting in this way since 1994, the spokeswoman added.
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