In an effort to close high-profile tax loopholes, Colorado Senator Ron Wyden has officially urged the Treasury Department and the Internal Revenue Service to clamp down on aggressive financial vehicles popularized by AQR, one of the world’s largest hedge funds.

The inquiry focuses on complex strategies used by major institutional investors to significantly reduce their tax liabilities. Lawmakers argue that these mechanisms push the boundaries of current tax laws, draining federal revenue and necessitating immediate regulatory intervention.

The Treasury and the IRS have not yet detailed their formal response to the senator’s request, but the pressure highlights ongoing scrutiny over how large financial institutions manage their tax obligations in an evolving regulatory landscape.