Should governments tax an investment that has increased in value even though its owner has never sold it?

That question sounds technical, but it reaches into one of the fundamental assumptions of modern investing.

Under the traditional capital-gains system, an investor generally pays tax when an appreciated asset is sold. Until then, the increase in value exists on paper but has not been converted into cash.

A tax on unrealized gains would change that framework.

Instead of waiting for a transaction, governments could tax increases in an asset's market value as they occur.

Supporters argue that this would address a major weakness in the existing system: extremely wealthy individuals can accumulate enormous amounts of wealth in appreciating assets while realizing relatively little taxable income.

Opponents counter that an unrealized gain is not necessarily spendable wealth. An asset can rise dramatically in one year and fall just as dramatically the next. Taxing the increase before the owner has actually sold anything could therefore create difficult liquidity and valuation problems.

The disagreement ultimately comes down to a fundamental question:

Should taxation follow economic wealth as it accumulates, or should it follow the realization of that wealth through a sale?

Context: Why This Matters Now

Wealth inequality has pushed the taxation of capital gains higher on the political agenda.

Traditional income taxation is relatively straightforward: wages, salaries, and other forms of income generate measurable cash flows. Asset appreciation is different.

Consider an investor who owns a company valued at $1 billion.

If the value rises to $1.5 billion, the investor has theoretically become $500 million wealthier. But no transaction has necessarily occurred, and the investor may not have $500 million in cash available.

Under a realization-based system, that appreciation generally remains untaxed until a taxable event occurs.

That distinction becomes particularly important for extremely wealthy households whose wealth is concentrated in businesses, stocks, real estate, and other appreciating assets.

The policy question is whether this structure allows some taxpayers to accumulate wealth indefinitely while delaying taxation.

Expert Perspectives

Elizabeth Warren: Tax Wealth Where It Accumulates

Senator Elizabeth Warren has been one of the most prominent political advocates for taxing wealthier households more aggressively.

Her argument is fundamentally about fairness.

If someone can experience enormous increases in wealth without generating conventional taxable income, a system based exclusively on realized income can produce a mismatch between economic prosperity and tax obligations.

From this perspective, taxing unrealized gains is an attempt to close that gap.

The policy is aimed primarily at extremely wealthy individuals rather than ordinary investors.

The argument is not simply that investments should be taxed more heavily. It is that the existing definition of taxable income may fail to capture how modern fortunes are actually created.

For Warren and other proponents, the objective is therefore redistribution as well as revenue.

A portion of rapidly accumulating private wealth could instead support public spending, infrastructure, healthcare, education, or other government priorities.

Larry Kotlikoff: Redesign the Incentives

Economist Larry Kotlikoff approaches the issue from an economic-design perspective.

The argument for taxing unrealized gains is that the existing system can create incentives to hold appreciating assets indefinitely rather than realize them.

If taxes are triggered only when an asset is sold, delaying the sale can also delay the tax.

A properly designed system could potentially reduce that advantage.

But even supporters recognize that design is critical.

An effective system would have to address questions such as:

1. How should privately held businesses be valued?
2. What happens when an asset falls after the taxpayer has already paid tax on its appreciation?
3. How would taxpayers pay a tax bill without selling the underlying asset?
4. How would losses be treated?
5. How frequently would assets be revalued?

The existence of these questions does not necessarily invalidate the concept.

It does demonstrate that taxing unrealized gains is substantially more complicated than simply applying a percentage to an investment account's annual increase.

Kevin Brady: Don't Tax Paper Wealth

Former Representative Kevin Brady takes the opposing position.

His central concern is liquidity.

An investor may own an asset worth significantly more than when it was purchased but have little cash available to pay a tax on that appreciation.

This becomes particularly complicated with privately held companies, real estate, or other assets that cannot easily be sold in small portions.

Brady also raises concerns about market behavior.

If investors know they will owe taxes on annual appreciation, they may sell assets sooner than they otherwise would.

That could reduce the incentive to hold investments for the long term and potentially introduce additional selling pressure into markets.

The issue becomes especially problematic during volatile periods.

An asset might appreciate significantly in one year, generating a tax liability, and then lose much of that value the following year.

That creates the possibility of taxpayers paying taxes on gains that later disappear.

The Core Problem: A Gain Isn't the Same as Cash

This is the strongest argument against a broad unrealized-gains tax.

Imagine buying an asset for $1 million.

One year later, its estimated value is $2 million.

Under an unrealized-gains tax, the $1 million increase could potentially become taxable even though you haven't sold the asset.

But where does the money to pay the tax come from?

You could sell part of the asset.

That introduces a circular problem: the tax itself can force the realization that the traditional system was designed to wait for.

For publicly traded stocks, this may be relatively manageable because shares are liquid.

For a private company, artwork, real estate, or another difficult-to-value asset, it becomes much harder.

This distinction is critical.

A policy that works relatively smoothly for publicly traded securities may be considerably more complicated when applied to illiquid assets.

The Strongest Argument for the Tax

The strongest argument is not that every investor should suddenly pay taxes every year on every increase in their portfolio.

It is that the existing realization system may be particularly advantageous for people whose wealth is concentrated in appreciating assets.

A wealthy individual may be able to:

1. own highly appreciating assets;
2. avoid selling them;
3. avoid triggering capital-gains tax;
4. borrow against those assets for liquidity;
5. continue allowing the assets to appreciate.

That can produce a significant difference between economic wealth and taxable income.

From the perspective of proponents, that is precisely the problem that tax reform should address.

The Strongest Argument Against It

The strongest argument against taxing unrealized gains is that market value is not the same thing as realized economic income.

An investment worth $10 million today might be worth $7 million next year.

If the investor is taxed on the $3 million increase that existed temporarily, the tax system has effectively treated a volatile paper gain as though it were permanent income.

That creates difficult questions about refunds, credits, losses, and administrative complexity.

It also potentially changes investor behavior.

Long-term investors could become more sensitive to annual tax liabilities rather than focusing exclusively on the long-term economics of their investments.

Editorial Synthesis

Where Experts Agree

There is more agreement than the political debate sometimes suggests.

1. Wealth inequality is a legitimate policy concern.
2. The existing tax system has advantages and disadvantages.
3. Design matters enormously.
4. Liquidity and valuation problems cannot simply be ignored.

The disagreement is primarily about whether the potential benefits justify the complexity and behavioral consequences.

Where Experts Disagree

The biggest disagreement concerns the appropriate definition of taxable wealth.

Warren's position emphasizes the reality of wealth accumulation: if an individual's assets rise enormously in value, that person has experienced a meaningful increase in economic power even without selling.

Kotlikoff focuses on designing a system capable of capturing that wealth more effectively while minimizing distortions.

Brady emphasizes the opposite problem: an increase in market value does not necessarily provide the taxpayer with cash, and taxation before realization could interfere with investment decisions.

These perspectives reflect two different principles.

Tax wealth as it accrues.

versus

Tax wealth when it becomes liquid and realized.

Why This Matters

The debate is bigger than whether billionaires should pay more taxes.

It concerns the architecture of investment itself.

The realization principle has historically provided investors with a valuable feature: they can hold an appreciating asset without owing tax on every fluctuation in its value.

That encourages long-term ownership and avoids forcing taxpayers to constantly monetize their investments.

But the same feature can also allow very wealthy individuals to defer taxation for extremely long periods.

The challenge for policymakers is therefore to address the second problem without destroying the advantages of the first.

A poorly designed unrealized-gains tax could create liquidity problems, distort investment decisions, complicate private-business ownership, and generate enormous administrative burdens.

A carefully targeted system, however, could potentially address some of the tax advantages associated with concentrated wealth without fundamentally changing how ordinary households invest.

The most important distinction may ultimately be who is being taxed and what assets are being targeted.

A policy aimed at extremely wealthy households holding enormous portfolios of highly liquid assets is fundamentally different from a universal annual tax on every household's retirement account or home appreciation.

That distinction often gets lost in the broader debate.

The Bottom Line

Taxing unrealized capital gains would not necessarily "break" long-term investing.

But a poorly designed version could create serious distortions.

The strongest case for the policy is that enormous increases in wealth can currently accumulate without corresponding taxable income.

The strongest case against it is that paper appreciation is volatile, sometimes difficult to value, and often impossible to convert into cash without selling the underlying asset.

The real policy challenge is therefore not simply deciding whether unrealized gains should be taxed.

It is deciding whose gains, which assets, at what threshold, under what valuation rules, and with what treatment for subsequent losses.

That is where the debate becomes much more consequential than the headline suggests.

The question isn't whether long-term investment should survive.

It is whether governments can redesign the tax system without undermining the very investment behavior that creates long-term capital in the first place.