Key takeaways
- A Section 351 exchange moves an appreciated portfolio into a new ETF with no tax today. Your cost basis and holding period carry over, and the embedded gain is deferred, not erased.
- You go from an old, tax-locked portfolio to a clean, diversified ETF without writing a check to the IRS. Diversification and tax deferral in a single step.
- The deferred gain rides along inside your new ETF shares. You decide when, or whether, to pay it, on your schedule rather than the market's.
The SpaceX IPO is coming, and a wave of newly liquid shareholders is about to go looking for a way to diversify without a giant tax bill.
The strategy they will hear about most is the Section 351 exchange. It came up at nearly every session of the Basis Northwest tax conference this year.
It is one of the most powerful tax-deferral tools available to investors sitting on large embedded gains, and it is more accessible than most people realize.
What a 351 exchange actually does
A Section 351 exchange, named for Section 351 of the Internal Revenue Code, lets a group of investors contribute securities into a newly launched exchange-traded fund (ETF) in exchange for shares of that fund, with no tax due at the time of the transfer.
Your cost basis, what you originally paid, and your holding period come along for the ride. The embedded gain is not realized. It is deferred inside your new ETF shares until you sell them.
The appeal is obvious. You go from an old, tax-locked portfolio to a clean, diversified ETF, and you do not write a check to the IRS to get there.
Transfer your appreciated shares tax-free into a diversified ETF, and defer the gain until you choose to sell.
Diversification without the tax bill
This is what makes the strategy so compelling. Normally, repositioning a low-basis portfolio means selling, realizing the gain, and handing a slice of it to the IRS before you can reinvest. A 351 exchange removes that toll.
You contribute your appreciated holdings into a launching ETF and walk out with diversified, liquid fund shares. No sale, no tax event, no check to the IRS this year. The embedded gain comes with you, carried inside the new shares, and stays deferred until you decide to sell, if you ever do.
A worked example
Consider an investor with $3,000,000 spread across a portfolio of long-held names. Cost basis is $1,000,000, leaving a $2,000,000 embedded gain.
Selling to rebalance would realize that $2,000,000 as a long-term gain. At the top 2026 federal rate of 20 percent plus the 3.8 percent net investment income tax, that is $476,000 of federal tax. Add California at its top 13.3 percent rate and you are near $742,000 due this year. (Illustrative, top brackets, 2026.)
Through a 351 exchange, the same investor contributes the portfolio into a launching ETF, owes nothing this year, and carries the $2,000,000 gain forward in the new shares. Same diversification goal. The tax bill is deferred, not paid.
A few things to plan around
A 351 exchange rewards planning. It requires timing: you generally contribute while a sponsor is seeding a new fund, not on any random Tuesday. A handful of ETF sponsors now run these conversions and publish education on the mechanics.
It is also a deferral, not an erasure. If you need cash today rather than diversification, or you expect to hold until death when a step-up in basis may wipe out the gain anyway, other paths may serve you better. For most investors carrying a large appreciated portfolio they want to diversify, the 351 exchange is hard to beat.
How STQ thinks about it
For a client heading into a major liquidity event, we do not start with the structure. We start with the portfolio: the cost basis, the holding period, the goals, and the timeline.
Then we match the tool to the situation. Often a 351 exchange is the elegant answer, the way to diversify and defer in a single, clean move, planned well before the shares are liquid.
The worst outcome is the common one: waiting until the stock is sellable, then selling in a panic and handing a quarter of the gain to two tax authorities that were never going to chase you for it.
Plan early. Diversify deliberately. Pay the tax on your schedule, not the market's.
If you are heading toward a liquidity event with a concentrated, low-basis position, it is worth mapping the sequence before the lockup ends. Send me a note and we can walk through it.
This is informational only and not personalized tax, legal, or investment advice.
Sources: 26 U.S. Code Section 351. Tax rates reflect top 2026 federal and California brackets and are illustrative only.
Frequently asked questions
How does a Section 351 exchange work?
A group of investors contributes securities into a newly launched ETF in exchange for shares of that fund, with no tax due at the time of the transfer. Your cost basis and holding period carry over, and the embedded gain is deferred inside the new ETF shares until you sell.
Do I ever pay the tax?
Yes, when you sell your ETF shares. The deferred gain rides along on your original cost basis. If you hold until death, your heirs may receive a step-up in basis that can erase the deferred gain under current law.
How is a 351 ETF exchange different from a traditional exchange fund?
An exchange fund is a partnership that typically locks your money up for about seven years and is limited to qualified purchasers. A 351 conversion gives you liquid ETF shares with no seven-year lock.
Does the SpaceX IPO timing matter?
Yes. A 351 contribution generally has to happen while a sponsor is seeding a new ETF, and you usually cannot transfer shares until the post-IPO lockup expires. Both argue for planning before the shares are liquid.
Who actually runs 351 conversions?
A handful of ETF sponsors now offer them and publish education on the mechanics. The structuring is best handled with a tax advisor.
Let's talk.
I'd love to walk through what a tax-efficient approach could look like for your specific situation.
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