WASHINGTON — Apple employs a group of affiliate companies located outside the United States to avoid paying billions of dollars in U.S. income taxes, a Senate investigation has found.

The world’s most valuable company is holding overseas some $102 billion of its $145 billion in cash, and an Irish subsidiary that earned $22 billion in 2011 paid only $10 million in taxes, according to the report issued Monday by the Senate Permanent Subcommittee on Investigations.

The strategies Apple uses are legal, and many other multinational corporations use similar tax techniques to avoid paying U.S. income taxes on profits they reap overseas. But Apple uses a unique twist, the report found. The company’s tactics raise questions about loopholes in the U.S. tax code, lawmakers say.

The spotlight on Apple’s tax strategy comes at a time of fevered debate in Washington over whether and how to raise revenues to help reduce the federal deficit. Many Democrats complain the government is missing out on collecting billions because companies are stashing profits abroad and avoiding taxes. Republicans want to cut the corporate tax rate of 35 percent and ease the tax burden on money U.S. companies make abroad. They say the move would encourage companies to invest at home.

Apple CEO Tim Cook, the company’s chief financial officer and its tax chief are scheduled to testify and explain the company’s tax strategy at a hearing by the subcommittee today.

The company refuted the subcommittee’s assertions in testimony prepared for the hearing and released to the public Monday evening. Apple said it employs tens of thousands of Americans and pays “an extraordinary amount” in U.S. taxes, citing the roughly $6 billion it paid in fiscal 2012.

Apple “complies fully with both the laws and the spirit of the laws,” the testimony says. “And Apple pays all its required taxes, both in this country and abroad.”

“Apple does not use tax gimmicks,” the statement says. The company insisted it does not, as the subcommittee asserts, move its intellectual property rights into offshore tax havens and use it to sell products back into the U.S. to avoid taxes.

The company has made clear that given current U.S. tax rates, it has no intention of repatriating its overseas profits to the U.S. Apple reiterated in its testimony its support for comprehensive tax reform as a way to support economic growth and boost U.S. companies’ competitiveness.

The subcommittee also has examined the tax strategies of Microsoft, Hewlett-Packard and other multinational companies, finding they too have avoided billions in U.S. taxes by shifting profits offshore and exploiting weak sections of the tax code. Microsoft has used “aggressive” transactions to shift assets to subsidiaries in Puerto Rico, Ireland and Singapore, in part to avoid taxes.