Box 3 2028: How Dutch Investors Are Repositioning Now

If the Wet werkelijk rendement box 3 survives the Senate, January 1, 2028 will be the first day the Belastingdienst taxes you on stock gains you haven't sold. Not interest. Not dividends. The number on your screen going up.

That's a real change in how a Dutch portfolio needs to be run, and it's why an ING survey in March 2026 found 9% of private investors already cutting risk exposure two years ahead of implementation, with close to three-quarters saying they'll likely adjust strategy once the law lands. For the mechanics of how Box 3 got here (the 2021 Kerstarrest, the botched fix, the missed deadlines), see our full history of the Box 3 saga. This article is about what to actually do with your portfolio between now and then.

What Changes for a Portfolio, Specifically

Right now, Box 3 taxes a fictional return on your total capital, regardless of what your actual investments did. Under the 2028 proposal, most private investors move to a flat 36% tax on real returns, split into two tracks:

• Default track (mark-to-market): listed stocks, bonds, ETFs, and crypto get revalued every December 31. Any increase in value is taxed at 36%, even if you never sold a share.
• Realization track: real estate and qualifying startup/scale-up shares are only taxed when you sell, gift, or inherit them.

The annual tax-free allowance also changes shape. Instead of exempting a chunk of your total wealth, the new system exempts the first €1,800 of return per person, then taxes everything above it. Losses over €500 in a year carry forward indefinitely against future gains, which the current system doesn't allow at all.

Put plainly: a portfolio that's up 18% this year, roughly where the AEX/NL25 sits year-over-year as of July 2026, would generate a real cash tax bill under the new rules even if every share stayed in the account.

Why This Changes How You Should Think About Rebalancing

Under fictitious returns, selling a winner to rebalance doesn't create a Box 3 tax event, since the tax was never tied to what you actually sold. Under mark-to-market, that changes the calculus, but not in the direction most people assume.

Once unrealized gains are taxed annually regardless of whether you sell, rebalancing itself stops being a tax decision. You're already paying tax on the paper gain whether you trim the position or not. That actually removes a friction that keeps a lot of Dutch investors from rebalancing today. If you've been letting winners run because selling felt like it triggered something, the new system removes that excuse, since the tax already happened at year-end regardless.

What does matter more: timing large purchases and knowing your December 31 valuation before it happens, not scrambling in January. If you're not already tracking day-to-day allocation drift, a rebalancing routine tied to a real trigger, not a market call, becomes more useful under mark-to-market, not less, because you'll want to know your exposure and its approximate valuation well before the tax clock resets each year.

The Liquidity Problem Nobody's Pricing In Yet

Here's the part that gets missed. A mark-to-market gain is taxed in cash, but the gain itself is not cash. If your portfolio is up €40,000 on paper and mostly invested in illiquid or single-position stock, you may owe roughly €14,400 in tax (36% above the exemption) without having €14,400 sitting anywhere.

That forces a choice most Dutch investors haven't had to make before: sell part of a position specifically to fund a tax bill on a gain you didn't realize by choice. And that sale can itself generate a further realized gain, which is its own taxable event. It's not double taxation in a technical sense, but it compounds the cash-flow problem in a bad year for liquidity.

The practical takeaway: if 2028 holds, keeping some cash buffer, or holding a portion of the portfolio in easily-sold, low-friction positions, stops being optional housekeeping and starts being part of the strategy. Investors who only ever check total portfolio value once a quarter are going to be caught flat by a bill they can't see coming, which is exactly the kind of thing that's easy to miss without visibility into actual, not fictitious, performance throughout the year rather than just at tax time.

Should You Sell Before 2028?

Selling now purely to dodge the new system is usually the wrong move, for three reasons.

First, selling today realizes the gain under the current fictitious-return system, where you're taxed on assumed returns regardless of what you sell. You don't avoid Box 3 by selling early. You just give up two more years of compounding for no tax benefit.

Second, the law hasn't passed the Senate. Box 3 reform has missed three implementation deadlines already going back to the original 2025 target. Restructuring a portfolio around a law that might change again, or slip again, is a bet on legislative certainty that this specific reform has not earned.

Third, the mark-to-market track applies to future gains from the date it takes effect, not retroactively to gains you already hold. There's no tax advantage to realizing today what you'd only be taxed on going forward anyway.

Where the calculation does shift: dividend-paying stocks versus pure growth stocks. Dividends are already realized income and get taxed as such either way. A pure growth stock with no distributions concentrates its entire return into that one annual mark-to-market snapshot. If two positions offer similar total return expectations, one paying out along the way and one compounding silently, the mark-to-market system narrows the after-tax gap between them in a way the old system didn't. That's a real portfolio-construction input, not just a tax footnote.

The Real Estate and Startup Carve-Out

The realization-only track for real estate and qualifying startup or scale-up shares is the one clear planning lever in the current draft. Assets on that track are taxed like the rest of Europe already taxes capital gains: when you sell, not while you hold. For an investor comfortable with illiquidity and a longer horizon, that's a meaningful structural difference from a portfolio of listed ETFs.

This isn't a recommendation to abandon liquid markets for property or angel investing. Both carry their own risk and liquidity tradeoffs that have nothing to do with Box 3. But if you were already considering a real estate allocation or startup investment for other reasons, the tax treatment under the 2028 draft tilts modestly in that direction compared to holding the equivalent value in listed shares.

On Emigration

Wealth managers, including advisors at ABN Amro MeesPierson, report clients bringing up emigration more often since the Senate vote loomed. It's worth naming honestly rather than pretending it isn't part of the conversation. It's also a decision with its own exit-tax rules, residency requirements, and life disruption that dwarf a marginal Box 3 rate change for the vast majority of portfolios. Nobody should restructure their life around a tax law that hasn't cleared the Senate. If you're seriously weighing it, that's a conversation for a cross-border tax advisor, not a blog post.

What to Actually Do Between Now and 2028

None of this is financial or tax advice, and the specifics of your situation, your broker, your other Box 3 assets, matter more than any general rule. But three habits are worth building now regardless of how the Senate vote lands:

1. Know your real return, not your assumed return. The entire point of the new system is that it taxes what actually happened to your money. Investors who've spent years thinking in Box 3's fictitious-return terms will need to start thinking in real, position-by-position return terms instead.
2. Build a cash or liquid-asset buffer sized to a plausible tax bill, not to your current spending needs. A good year in the market is precisely when this bill would be largest.
3. Revisit your allocation between dividend and growth positions with the mark-to-market track in mind, not as an overhaul, but as one more input alongside the ones you already use.

The Senate hasn't voted. The rules could still shift before 2028, or slip to a later date again. But the investors who come out ahead won't be the ones who panicked in 2026 or ignored it until December 2027. They'll be the ones who already know what their portfolio is actually doing, year over year, well before the Belastingdienst asks.

Sources

• Bill on the Box 3 Actual Return Act adopted by the House of Representatives, Deloitte Netherlands
• Netherlands: Transition to new Box 3 wealth tax regime, KPMG
• Netherlands' Plans for Tax on Wealth Spark Fierce Opposition, Bloomberg