Both let you diversify a concentrated position without a taxable sale. They are built completely differently, and the wrong one locks up capital you needed.
If you hold a single position that has grown into most of your net worth, you already know the bind. Too risky to keep, too expensive to sell. Two structures let you diversify out of it without triggering the gain today: a Section 351 exchange and an exchange fund. People hear "diversify without tax" and assume they are the same tool. They are not.
Both defer the capital gain, both leave you diversified, and neither is a taxable sale. That is where the similarity ends. The difference is what you contribute, how long your money is locked up, and how liquid you are on the other side.
A Section 351 exchange rolls an appreciated portfolio into a newly formed ETF in return for shares of that ETF. No sale, so no tax today. Your basis carries over, and the gain is deferred until you eventually sell the ETF shares.
The catch is the entry requirement: the pool of contributed securities has to already be diversified. Broadly, no single holding can be more than 25% of the contributed value, and the top five cannot exceed 50%. You cannot hand over one concentrated stock and call it done. This makes a 351 a fit when you have a portfolio of appreciated names, or can pool with others, rather than a single ticker. What you get in return is real liquidity: ETF shares you can sell on your own schedule.
An exchange fund solves the opposite problem. You contribute your single concentrated position into a large partnership pooling many investors' concentrated stock, and you receive a pro-rata interest in the whole diversified pool. The gain is deferred, basis carries over, and the diversification happens the moment you contribute.
The price of that is time and liquidity. Exchange funds carry a required holding period, typically around seven years, before you can redeem into a diversified basket of stock. They are generally limited to accredited or qualified-purchaser investors, and the fund itself has to hold a slice of illiquid assets to qualify. It buys instant diversification on a single name, at the cost of locking that capital up.
Same goal, opposite designs. One gives you liquidity; the other trades liquidity for instant diversification on a single name.
Start with two questions: what are you contributing, and when do you need the money back. If you already hold a spread of appreciated positions and want to stay liquid, the 351 is usually the cleaner path. If your problem is one dominant low-basis stock and you genuinely will not touch that capital for years, an exchange fund does something the 351 cannot: diversify a single name in one step.
Neither is a default. Both carry costs, eligibility rules, and structural risk, and both need to be weighed against simpler tools, like a direct-indexing glide path that trims the position gradually while harvesting losses to offset the gain. The full menu for a position like this is in our guide to concentrated stock positions.
We do not lead with the product. We start with your basis, your bracket, your timeline, and how much of that capital you actually need liquid over the next decade, then model the structures against each other and against just selling in a low-income year. Often the answer is a combination, sequenced across tax years and coordinated directly with your CPA. The structure serves the plan, not the other way around.
For informational and educational purposes only. Section 351 exchanges and exchange funds involve significant complexity, costs, eligibility requirements, and risks, and are not suitable for everyone. Rules and thresholds are summarized and simplified here and are subject to tax law, which can change. This is not personalized tax, legal, or investment advice. Consult a qualified professional about your situation.
One position carrying most of your net worth? We will model a 351, an exchange fund, and the simpler alternatives against your actual basis and timeline, and tell you which one earns its place.
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