The U.S. Internal Revenue Service is scrutinizing the novel tax structure of the popular BOXX ETF, a move that could erase its primary advantage for high-income investors.
The $11.4 billion Alpha Architect 1-3 Month Box ETF (NYSEARCA: BOXX), a fund designed to deliver Treasury-like yields with a significantly lower tax burden, is facing questions from the IRS over the validity of its core strategy. The agency's scrutiny threatens to unwind the tax benefits that have attracted billions from investors in high-tax states.
"The entire value proposition relies on tax arbitrage," ETF.com wrote in a November 2025 analysis, noting that the fund's "long-term viability hinges on whether regulators will address its tax classification strategy." The structure has never been formally blessed by the IRS.
BOXX has returned 4% over the past year by using complex options contracts known as box spreads to replicate the performance of short-term U.S. Treasury bills. Instead of paying out interest as taxable income, gains accumulate as price appreciation in the ETF shares. For a high-earner in California, this could translate to tax savings of $7,000 annually on a $500,000 investment held over a year, compared to a traditional money market fund.
A negative ruling from the IRS could force a retroactive reclassification of all gains as ordinary income. Such a move would not only eliminate the fund's primary appeal but could also leave current and former shareholders with unexpected back-tax liabilities and potential penalties, fundamentally altering the risk profile of what is marketed as a cash alternative.
The fund’s engine is the box spread, a combination of four options on the S&P 500 that creates a fixed, low-risk return equivalent to the risk-free rate. Unlike a Treasury ETF that receives interest and distributes it as ordinary income, BOXX uses the in-kind redemption mechanism common to ETFs to flush out embedded gains without triggering a taxable event for remaining shareholders.
This structure is what allows for the conversion of would-be income into long-term capital gains, taxed at a federal rate of 20% plus a 3.8% net investment income tax, versus ordinary income rates that can exceed 50% when combined with state taxes. However, this complex process comes at a cost. The fund's 0.19% expense ratio is more than double the 0.09% fee of the iShares 0-3 Month Treasury Bond ETF (NYSEARCA: SGOV), a straightforward alternative for state-tax-free Treasury exposure.
The regulatory risk is not new. Financial commentators have been flagging the issue for years. In December 2024, Jim Dahle of the popular blog White Coat Investor advised readers to "wait two to three years to see how the IRS addresses its tax strategy."
These concerns were amplified in August 2024 when the fund, which already had nearly $4 billion in assets, made a small but "unintended" taxable distribution. While the amount was minor, the event demonstrated that the complex structure could leak under certain conditions, undermining its core promise of zero distributions.
For investors, the IRS inquiry transforms a perceived tax loophole into a tangible financial risk. While alternatives like the Janus Henderson AAA CLO ETF (NYSEARCA: JAAA) offer higher yields taxed as ordinary income, and municipal money market funds provide federal tax-free income, none offer the specific capital gains conversion that BOXX does. The question now is whether the IRS will allow that conversion to continue.
This article is for informational purposes only and does not constitute investment advice.
