A lawsuit filed by a group of accountants and lawyers alleges that investors overpaid billions of dollars in taxes when life insurance companies such as Principal Financial Group Inc. reorganized into publicly traded corporations, the Associated Press reported.

The lawsuit, led by Charles Ulrich, a retired accountant in Baxter, Minn., charges that the Internal Revenue Service overtaxed stock and cash that investors received when mutual life insurance companies reorganized over the past 15 years. More than 30 companies, including Prudential Financial Inc., MetLife Inc., and Principal, have demutualized since the late 1990s.

A trial is scheduled to start June 18 in the Court of Federal Claims, which tax experts say the IRS is likely to lose based on a ruling by the same court last November that essentially said the IRS’s logic was not valid. Taxpayers can file a claim before the case is decided.