IRS rules "351 conversion" ETF swaps are taxable and flags box-spread funds; notice warns action could be retroactive

The Treasury Department and the IRS moved on Monday against a set of fast-growing fund strategies that let investors defer or reshape their tax bills. Revenue Ruling 2026-20 says one popular ETF maneuver, the "351 conversion," is a taxable sale when it is done as part of a plan. A companion Notice 2026-62 lists several more strategies the agencies say "may be inconsistent with the purpose and proper application" of the tax rules, and asks for comments by October 28, 2026.

What the ruling actually says

In a 351 conversion, an investor with a portfolio full of unrealized gains contributes those securities to a newly formed ETF in exchange for ETF shares, which is normally tax-free. The ETF then hands some of those same securities to an authorized participant, the market-making firm that creates and redeems ETF shares, and ends up holding a different portfolio. The investor has effectively swapped a concentrated set of winners for a diversified fund without paying tax.

The IRS now says that when those steps are part of one plan, the ETF is "merely a conduit" and the investor is treated as having sold the securities to the authorized participant in a taxable exchange. The ruling says the result is the same whether one investor or many are involved.

The other strategies on the list

The notice does not rule on these yet, but it describes each one and says the agencies are considering regulations, further rulings, or labeling them a "transaction of interest" or "listed transaction," which brings disclosure duties and penalties. The list includes:

• Partnership exchange funds that feed into a 351 conversion.
• Box spread funds: ETFs that use four options to earn something close to a short-term interest rate, then push out the options carrying gains through redemptions so the fund reports no current income.
• Record date strategies, where one ETF redeems its stake in another just before a dividend record date.
• Income test workarounds for funds holding commodities or digital assets.
• Derivative trades by tax-aware funds, including currency forward elections, straddles mixing currency forwards with futures, and selective swap terminations, used to turn losses or gains into a more favorable character.

The sentence that matters most: retroactivity

Most coverage will focus on the ETF ruling. The bigger risk for anyone already in these trades sits in the notice's first section: any guidance "could apply prospectively only or retroactively to transactions that already have taken place at the time the guidance is issued." A footnote cites the part of the tax code that lets Treasury make a rule retroactive "to prevent abuse." The agencies also say the IRS may challenge these strategies on audit under existing law, before any new rule is written. We found no start date or grandfather clause in the ruling itself.

The notice does try to draw a line. It says guidance will "target specific abusive transactions" and respect "conventional, long-established tax planning," such as seeding a fund with assets that fit its stated strategy and keeping them.

Who this hits

People who used a 351 conversion to diversify. Think of an early employee or a founder holding a stock that has gone up tenfold. The conversion was sold as a way to diversify without a tax bill. Under Monday's ruling, if the fund's redemptions were part of the plan, that bill may still be owed. Anyone who did one should take the ruling to their tax adviser now, not at filing time.

Businesses parking cash in "T-bill alternative" ETFs. Box spread funds were built to earn a Treasury-bill-like return while deferring the tax into a later capital gain. For scale, the three-month Treasury yielded 4.28% on Monday, according to Treasury's daily data. On $500,000 of idle business cash, that is about $21,400 a year of return (our calculation), which is normally taxed as interest in the year it is earned. The whole appeal of a box spread fund is moving that tax to later. If the IRS eventually rejects the redemption step, that advantage could disappear, and possibly for past years too.

ETF sponsors. Fund firms that built products around these structures now face an open comment period and the prospect of disclosure rules. Watch for sponsors to comment by October 28 and for any changes to how these funds describe their tax treatment.

Nothing in the notice changes the ordinary in-kind redemption process that standard index ETFs use to limit capital-gains payouts. The agencies are targeting what they call "atypical usage" of it.

Sources: IRS Notice 2026-62; Revenue Ruling 2026-20; Current Federal Tax Developments; U.S. Treasury yield data. The $500,000 example is our calculation. This is general information, not tax or investment advice.