IBM has revealed the US Securities and Exchange Commission is investigating the software giant's accounts, looking into revenue recognition with certain deals in the United States, Britain and Ireland.
The company said it learned of the investigation in August and was cooperating with the SEC, but did not disclose what deals were being probed.
"IBM has a rigorous and disciplined process for the preparation of its financial statements and the reporting of revenue," an IBM spokesman said..
IBM has been a subject of several SEC probes in the past, including an investigation in 2013 on how it reported revenue from cloud computing business. The regulator later decided not to recommend any action following the investigation.
Shares of the world's largest technology services company fell as much as 4.4 percent to a five-year low of US$137.33.
IBM posted a bigger-than-expected drop in third-quarter revenue and cut its full-year profit forecast last week as a stronger US dollar accentuated weakness in demand from China and emerging markets.
Separately, IBM also authorised a US$4 billion share buyback today, in addition to US$2.4 billion remaining from a previous share repurchase program announced in October last year.
Up to today's close, IBM's stock had dropped about 10.5 percent this year.