WASHINGTON — A Senate investigation has found that hedge funds — including James Simons’ Renaissance Technologies and Steven Cohen’s SAC Capital Advisors — have claimed billions of dollars in tax savings through complex financial structures.

Between 1998 and 2013, more than a dozen hedge funds conducted hundreds of billions of dollars in trades using hundreds of structures, known as “basket options,” created by Barclays and Deutsche Bank, according to the Senate Permanent Subcommittee on Investigations.

“These banks and hedge funds involved in this case used dubious structured financial products in a giant game of ‘let’s pretend,’ costing the Treasury billions and bypassing safeguards that protect the economy from excessive bank lending for stock speculation,” said Sen. Carl Levin, D-Mich., the chairman of the Senate subcommittee.

The findings — based largely on an investigation into the two biggest users of the products, Renaissance and George Weiss Associates, a multistrategy hedge fund based in New York — will be the subject of a Senate panel hearing today in Washington. Peter Brown, co-chief executive of Renaissance, and senior executives from Barclays and Deutsche Bank are scheduled to testify.

The basket options were structured as accounts that allowed hedge funds to bypass taxes on short-term trades. Barclays and Deutsche Bank used the options to build special accounts for their hedge fund clients in their own names and claimed they owned the assets when it was, in fact, the hedge fund clients that exercised full control of the assets, determining each trade and reaping all the profits, the investigation found.

Hedge funds like Renaissance Technologies would wait just after a year to “exercise the options,” claiming the profits should be taxed at a lower income tax rate for long-term capital gains on assets.

The hedge fund says that the options provided leverage and protection against downside loss and should be taxed at long-term rates rather than short-term rates because they were held for more than a year.