Netherlands Unrealized Capital Gains Tax: What the New 36% Box 3 Rule Really Means

The Netherlands is preparing to do something almost no other country does: tax investment gains that investors haven’t actually collected yet. Under a new law passed by the Dutch House of Representatives, residents will owe 36% tax on unrealized capital gains starting in 2028 meaning a stock, crypto, or bond portfolio that simply goes up in value on paper can trigger a real, cash tax bill, even if nothing was ever sold.

This guide breaks down exactly how the Netherlands unrealized capital gains tax works, who it applies to, who’s exempt, and why it has sparked so much debate among investors, founders, and economists.

Quick Answer

Starting January 1, 2028, Dutch tax residents will pay a flat 36% tax on the actual annual return from savings and investments held in “Box 3” including, for the first time, increases in the value of assets like stocks, bonds, and cryptocurrency that have not been sold. The law is called the Wet werkelijk rendement box 3 (“Actual Return in Box 3 Act”). Real estate and most startup shareholdings are taxed differently, only when a gain is actually realized. The bill passed the Dutch House of Representatives on February 12, 2026, and awaits Senate approval before it can take effect.

Why the Netherlands Is Reforming Box 3

Dutch personal income tax is split into three “boxes.” Box 3 covers income from savings and investments. For years, Box 3 taxed investors on a deemed (assumed) return rather than their actual return — a system the Dutch Supreme Court ruled unconstitutional starting in December 2021 for violating property rights and equal treatment principles.

The government’s fix is the Actual Return in Box 3 Act, which replaces assumed returns with a system based on real, “mark-to-market” investment performance. The catch: because most liquid assets don’t generate a taxable event every year, lawmakers decided to tax the paper increase in value annually, not just gains from a sale. The Dutch State Secretary for Taxation has acknowledged that a purely realization-based system was the government’s preferred approach but wasn’t seen as workable in time for the 2028 rollout, since it would create a bigger short-term hit to tax revenue.

How the 36% Tax on Unrealized Gains Works

Here’s the mechanism in plain terms:

• Each year, your Box 3 assets are valued on January 1 and again on December 31.
• The increase in value over that period plus any income like interest, dividends, or rent counts as your “actual return.”
• You pay 36% on that return above a tax-free allowance of €1,800 per person annually.
• If your assets lose value the following year, you can carry the loss forward indefinitely to offset future Box 3 gains but that doesn’t refund a tax bill you already paid.

Worked Example

Imagine a Dutch investor holds a stock or crypto portfolio worth €50,000 on January 1. By December 31, it’s worth €100,000 a €50,000 unrealized gain. After the tax-free allowance, the investor owes 36% tax on the remaining taxable gain, payable the following spring.

The problem critics point to: if the market drops sharply before the tax bill is due the way crypto and growth stocks often do the investor still owes tax calculated on the higher year-end value. They may be forced to sell assets at a loss just to cover a tax bill on money they never actually banked.

Which Assets Are Taxed Differently

Not everything in Box 3 is taxed on unrealized gains. Two major carve-outs matter a lot:

Asset type	How it’s taxed
Stocks, bonds, crypto, savings	Annual tax on unrealized + realized gains (mark-to-market)
Real estate	Only taxed when sold or transferred (realized gains); rental income taxed annually as received
Qualifying startup shares (under certain conditions)	Only taxed on dividends annually; capital gains taxed at sale, not on paper growth

For real estate, this mirrors how most capital gains taxes work elsewhere in the world: you pay when you actually cash out.

The Startup and Founder Problem

The startup exemption is where the policy gets complicated for early employees, angel investors, and equity holders. To qualify, a company generally needs to be young and below a revenue threshold set in the legislation. Founders holding 5% or more of their own company are treated separately and are largely shielded, and qualifying angel investors also receive relief. But once a startup grows past the qualifying threshold exactly the outcome any investor wants the exemption can lapse, and years of accumulated, untaxed paper gains can become taxable at once.

That creates a liquidity problem unique to private companies:

• Private company shares usually can’t be sold freely shareholder agreements, transfer restrictions, and rights of first refusal are common.
• There’s no public market to quickly sell a small slice of shares to cover a tax bill, unlike a public stock.
• Investors may need to borrow against illiquid shares to pay a tax on value they haven’t received, assuming a bank is even willing to lend against that collateral.

Critics argue this discourages exactly the kind of early-stage, high-risk investment that helps startups scale — because backers face a real cash tax exposure tied to a company’s success on paper, long before any actual liquidity event.

Where the Law Stands Now

• February 12, 2026 – The bill passed the Dutch House of Representatives (Tweede Kamer).
• Pending – Senate (Eerste Kamer) approval is still required before the law is finalized.
• January 1, 2028 – Target effective date if approved.
• A newer coalition of major Dutch parties has already signaled it wants to eventually move to a pure realized-gains model, with draft legislation possibly following by Budget Day 2028 — meaning the current unrealized-gains version may end up being a transitional system rather than a permanent one.

The Core Debate

Supporters’ case: A system based on actual returns is fairer and more constitutionally sound than the old deemed-return model, and taxing gains annually closes a loophole where wealthy investors could defer tax indefinitely by never selling.

Critics’ case: Taxing unrealized gains taxes value that may never materialize, forces investors to sell assets sometimes at a loss purely to fund a tax bill, and sends a signal that could push capital and entrepreneurs toward jurisdictions with lighter treatment of investment gains. Some point to past examples, like France’s wealth-tax-driven business departures in the late 1990s, as a cautionary precedent. Most European countries only tax capital gains when an asset is actually sold, which puts the Dutch approach in a small minority globally.

Both sides agree on one thing: this is one of the most closely watched tax experiments in Europe right now, and its outcome will likely shape how other countries think about taxing wealth in the years ahead.

FAQ

What is the Netherlands unrealized capital gains tax?

It’s a new Dutch tax law (Wet werkelijk rendement box 3) that will tax residents 36% annually on the actual return from savings and investments including increases in the value of stocks, bonds, and crypto that haven’t been sold starting January 1, 2028, pending final Senate approval.

When does the Netherlands start taxing unrealized gains?

The target start date is January 1, 2028. The bill passed the Dutch House of Representatives on February 12, 2026, but still needs Senate approval before becoming final law.

Is real estate taxed on unrealized gains in the Netherlands?

No. Real estate is taxed only when it’s sold or transferred (a realized gain). Rental income is still taxed annually as it’s received.

Are startup founders and investors exempt from the unrealized gains tax?

Founders holding 5% or more of their own qualifying company, and qualifying angel investors, are largely shielded under separate rules. However, once a startup grows past the qualifying size or age threshold, previously untaxed paper gains can become taxable, which creates cash-flow challenges since private shares are hard to sell quickly.

What is the tax-free allowance under the new Box 3 rules?

Individuals get a tax-free return allowance of €1,800 per person per year before the 36% rate applies.

Can losses be carried forward under the new system?

Yes. Losses within Box 3 can be carried forward indefinitely to offset future Box 3 gains, though this doesn’t reimburse tax already paid in a prior year.

Why is this tax controversial?

Because it taxes paper gains that could disappear before an investor ever cashes out, potentially forcing asset sales to cover a tax bill on money that was never actually received. Critics also worry it could push investors and entrepreneurs to relocate to countries with more favorable capital gains treatment.

Does any other country tax unrealized capital gains this way?

It’s rare. Most European countries and most countries globally only tax capital gains once an asset is sold (a realized gain), which is what makes the Dutch approach unusual on the world stage.

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This article summarizes publicly reported details of the Netherlands’ Box 3 tax reform (Wet werkelijk rendement box 3) as of August 2026. The legislation had passed the Dutch House of Representatives but was still pending Senate approval at time of writing, and details may change before the law is finalized. This is general information, not tax or financial advice — consult a licensed Dutch tax advisor for guidance on your specific situation.

Sources:

• IMI Daily — Dutch Lawmakers Approve a 36% Tax on Unrealized Crypto, Stock, and Bond Gains
• Crypto Briefing — Dutch House passes 36% tax on unrealized crypto and investment gains
• Archipel Tax Advice — Box 3 Reform (2028) Explained
• NTL International — Netherlands Box 3 Reform: Structural Shifts and the 36% Tax