Institutional investors are harvesting ETF losses for tax purposes, then placing their assets in highly correlated funds -- regardless of so-called wash-sale restrictions, a new study found.

In theory, IRS guidelines prohibit investors from buying "substantially identical" securities 30 days before or after selling them.

In practice, fund managers, pensions, insurance firms, endowments and other institutional investors "engage in substantial swapping" of ETFs with holdings that are 99% or more the same thing to the tune of $417 billion in assets since 2001 and $106 billion in 2022 in transactions that "seem to lack economic substance beyond harvesting capital losses," according to a working academic paper released this summer and revised last month by four professors of business and management. The findings, which echo those of another working paper from earlier this year, shed more light on how ETFs help financial advisors and their clients offset the taxes on capital gains by booking losses in their portfolios.

"While the economic intent of the wash sale rule is straightforward, significant uncertainty remains as to the permissibility of tax deductions achieved through ETF swaps," the report's authors -- Michael Dambra of the University of Buffalo and Andrew Glover, Charles M.C. Lee and Phillip Quinn of the University of Washington -- wrote in the introduction. "Specifically, the IRS has not ruled on what constitutes a 'substantially identical' security, leaving financial advisors to navigate a foggy legal landscape. Some advisors seem to take the regulatory silence as tacit permission to swap ETFs that hold identical securities or that are even benchmarked to the same index (e.g., Lasser 2011). Others argue that if an investor's economic position has not changed after swapping ETFs, the spirit of the wash sale rule has likely been violated (e.g., Fischer 2010). Against this backdrop of legal uncertainty, the extent to which investors engage in tax avoidance through ETF wash sales remains largely unknown."

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Representatives for the SEC declined to comment on the report's conclusions and referred questions to the IRS, which didn't provide a response.

The findings essentially "confirmed what all of us expected," but "what was striking about the study was being able to demonstrate that the loss harvesting was material enough to be measured," said Steve Rosenthal, a senior fellow at the Urban-Brookings Tax Policy Center, a nonpartisan think tank.