Financial Systems Do Not Only Tax Money

Yesterday I wrote about the mathematics of taxing unrealized gains in the Netherlands.

Today I want to step back from the numbers.

Because tax systems do not only collect revenue.

They shape behavior.

The proposed reform of Box 3 introduces taxation on annual value increases of investments, even when no sale has taken place. Whether one agrees with it or not, the more interesting question is this:

What does this change in how people think?

When investors know that rising markets can generate a tax bill without generating cash flow, something subtle happens. The focus shifts from long-term ownership to short-term manageability. Risk is no longer evaluated only by market volatility, but also by tax exposure.

Some may decide to hold more cash.

Some may reduce exposure to growth assets.

Some may look for ways to structure investments differently.

A few may even reconsider where they hold their capital.

Not dramatically. Not overnight.

But quietly.

Incentives rarely produce loud revolutions.

They produce slow behavioral drift.

There is also the matter of liquidity. If unrealized gains trigger tax, investors may be forced to sell portions of their portfolio simply to pay the bill. That introduces friction into what would otherwise be a long-term compounding journey.

And friction changes culture.

Over time, a nation develops an investment character. Some countries encourage patient ownership and risk-taking. Others favor caution and capital preservation.

Neither is morally superior.

But they produce different outcomes.

The Netherlands is not a fragile economy. It is innovative, productive, globally connected. This reform alone will not determine its future.

Yet systems matter at the margin.

And at the margin is where long-term wealth formation either accelerates or slows down.

The deeper issue is not whether the government can tax unrealized gains.

The deeper issue is what kind of investment mindset the system rewards.

Because financial systems do not only tax money.

They tax behavior.

And behavior, compounded over decades, shapes a nation’s economic trajectory.