SAN FRANCISCO (Reuters) - The U.S. Securities and Exchange Commission is investigating how the International Business Machines Corp IBM.N recognized revenue for certain deals in the United States, Britain and Ireland, IBM said on Tuesday, news that sent its shares down 4 percent.

People walk past sign at the booth of IBM at the CeBIT trade fair in Hanover March 15, 2015. REUTERS/Morris Mac Matzen

IBM, the world’s largest technology services company, said it learned of the investigation in August and was cooperating with the SEC, but did not disclose what deals were being probed.

An IBM spokesman told Reuters the company had a “rigorous and disciplined process” for its reporting of revenue.

Shares of IBM fell as much as 4.4 percent to a five-year low of $137.33 and closed down 4 percent.

News of the SEC probe came a week after the company posted lackluster quarterly results and cut its 2015 profit forecast.

“It couldn’t come at a worse possible time because now the stock is at another 52-week low as a result of this,” said Belpointe analyst David Nelson.

He said, however, that the probe “doesn’t look like a massive smoking gun.”

“The investigation could be into warranty reserves, they could have recognized an item at the wrong time,” Nelson said.

IBM has been a subject of several SEC probes in the past, including a 2013 investigation on how it reported revenue from its cloud computing business. Regulators ended that probe without recommending any action. (reut.rs/1MqyJ4K)

Earlier this month, the SEC called financial reporting “a key enforcement priority” as it announced a series of enforcement actions for violations of federal securities laws.

Revenue recognition is how a company records revenue on its books, with discrepancies often arising depending on whether cash is received, or payments deferred. Accounting rules differ in the United States and in Britain and Ireland.

A May 2014 change in the accounting standard for revenue recognition has increased scrutiny by regulators. Some 60 percent of SEC actions from 1998-2007 focused on improper revenue recognition, according to a 2010 report by COSO, a committee with representatives from private-sector accounting and other professional groups that studies fraudulent financial reporting.

Separately, IBM also authorized a $4 billion share buyback on Tuesday, in addition to $2.4 billion remaining from a previous share repurchase program announced last October.

Shares of the IBM have dropped steadily in recent months, falling 21 percent since hitting a year high of 173.97 in April.

Last week, IBM posted a bigger-than-expected drop in third-quarter revenue and cut its full-year profit forecast as a stronger U.S. dollar accentuated weakness in demand from China and emerging markets.