Diversifying a Concentrated Stock Portfolio Tax-Free

Instead of selling your concentrated stock positions and paying a large tax bill to diversify, you can exchange them tax-free for a diversified portfolio

Case Study Summary

A Couple Diversified $1.9 Million of Concentrated Stock Without Paying $445,000 in Taxes, Preserving $4.5 Million More for Their Daughter

By using a tax-free 351 exchange, they swapped their concentrated positions for a diversified U.S. equity ETF without selling a single share

Background: Why Is a Concentrated Portfolio a Problem?

Concentrated positions can create massive amounts of wealth.

Many of the richest people in the world are only as rich as they are because they held large positions in companies that were once worth very little. If they had sold early to diversify, they would be nowhere near as wealthy as they are today.

But people tend to celebrate the Bezos and Musk outcomes and ignore the people who took the same risk and lost everything.

If most of your wealth sits in a handful of stocks, you might be a millionaire on paper. But if those companies go under, your wealth goes with them.

Most people who reach a certain level of wealth realize there's more value in protecting it than in risking all of it to grow it further.

So why don't they just sell and diversify?

Because selling comes with a large tax bill.

And the answer to that is a tax-free 351 exchange.

What Did the Client's Portfolio Look Like?

Let's look at a real client case.

A high-earning couple in their 60s had built up a large portfolio by buying and holding stocks like Netflix, Apple, Microsoft, and Berkshire for many years. Those positions were now worth nearly 5 times what they paid for them.

They didn't need the money. Between their pensions and Social Security, their retirement income was covered and their expenses were low.

Their goal was to leave the portfolio to their daughter, who would inherit it tax-free through step-up in basis.

The problem was concentration. Their top five holdings made up most of the portfolio:

Client's Top Portfolio Positions

Outside of cash, the portfolio was heavily concentrated in a few stocks. Holding it for 30 years just to avoid taxes meant taking on a lot of investment risk.

What Would It Cost to Sell and Diversify?

The stock portion of the portfolio was worth about $1.9 million.

Because the couple was still working and earning $500,000 a year, and lived in New Jersey with its high state tax rate, selling those positions would trigger a $445,000 tax bill.

 Table 1: The Tax Cost of Selling the Concentrated Portfolio

A $3.3 million portfolio is really worth about $2.9 million after taxes. Most people quote their net worth at market value, not after-tax value, and get a large surprise from the IRS when they sell.

That left the couple with two options:

1. Keep the concentrated portfolio and hope the concentration doesn't hurt them.
2. Pay the $445,000 tax bill today and diversify into an S&P 500 fund.

What Does That $445,000 Tax Bill Cost Over 30 Years?

Let's assume both portfolios earn 8% a year for 30 years.

Let's also compare two ways the money reaches their daughter: selling the portfolio in 30 years and giving her the proceeds, versus holding it until death so she inherits it with a stepped-up basis.

 Table 2: Keeping the Concentrated Portfolio vs. Diversifying It

There are two big takeaways here.

First, selling in 30 years costs $7.9–$9.5 million in taxes. Holding until death costs nothing, because step-up in basis wipes out the gain for their daughter.

Second, since their goal is for their daughter to inherit the portfolio, paying the $445,000 tax bill today to diversify leaves her with $4.5 million less ($33.6 million vs. $29.1 million).

That's the problem.

So how do you diversify without paying the tax?

What Is a 351 Exchange?

A 351 exchange lets you contribute your stock positions and ETFs to a new ETF tax-free, in exchange for shares of that ETF.

For this client, we exchanged the concentrated portfolio into a diversified U.S. equity ETF (AAUS) offered by Alpha Architect.

The couple got a diversified U.S. equity portfolio without paying the $445,000 tax bill.

Table 3: The Result of the 351 Exchange

The 351 exchange gives the couple the diversification they wanted with the after-tax result of never having sold.

Does My Portfolio Qualify for a 351 Exchange?

There are a few tests a portfolio has to meet:

1. The portfolio has to be worth over $1 million and held at Schwab or Fidelity.
2. It has to consist of liquid, exchange-traded securities (publicly traded stocks and ETFs, not mutual funds).
3. No more than 25% of the portfolio can be in a single position.
4. No more than 50% of the portfolio can be in five or fewer positions.

The client's portfolio didn't pass at first because 42% of it was in cash.

To fix that, we used the cash to buy an equal-weighted S&P 500 ETF (RSP). That turned the cash into an exchange-traded security and diversified the portfolio enough to qualify.

What Happens If I Need to Sell Later?

Each position in the original portfolio is exchanged for its own tax lot in the new ETF, and each lot keeps its original cost basis.

That means if the client ever needs income, they can choose which lots to sell.

They would start with the lots that have little or no gain, which can be sold with no taxes owed. They would save the lots with the largest gains, like one lot with a 2,895% unrealized gain, for last, or never sell them at all.

Is This Worth the Effort?

About 20 hours of planning and paperwork saved the couple $445,000 in taxes today and should result in over $4 million more for their daughter.

That's the equivalent of earning an extra 0.52% of return every year, just from day-one financial planning.

What About the Estate Tax?

Step-up in basis avoids income taxes, but it doesn't avoid the estate tax.

The more the portfolio grows, the more likely it is to exceed the estate tax exemption, currently $30 million per couple in 2026. Anything above that is taxed at 40% at death.

And exemptions don't stay put. In 1997, the exemption was about $1.2 million per couple and the rate was 55%.

That's why the next step for this client is moving assets outside of the estate, so their daughter can avoid both income and estate taxes. We cover that in our article, "Navigating the Estate Tax Effectively."

Who This Strategy Is Best For

• ✓Corporate executives with large equity compensation packages
• ✓Founders or early employees with low-basis company stock
• ✓Investors with concentrated positions in a single security
• ✓Individuals who have experienced significant stock appreciation
• ✓Anyone whose net worth is disproportionately tied to one asset