Box 3 of the Dutch income tax system covers income from savings and investments — what other countries would call a wealth tax. For most expats with modest savings, the amounts involved are small. But for expats with substantial investment portfolios, foreign property, or pension assets, Box 3 can become the largest single component of their Dutch tax bill. The system has been under legal challenge for nearly a decade, and the rules in force in 2026 are a temporary patch that will eventually be replaced.
The original system
Until 2017, Box 3 worked by assuming a fixed deemed return on your total assets (typically 4 per cent) and taxing that deemed return at 30 per cent. The actual return on your assets — whether you held cash earning 0.5 per cent or stocks earning 8 per cent — was irrelevant. This system was repeatedly challenged in Dutch courts on the grounds that the deemed return bore no relationship to reality, particularly for savers holding cash during the zero-interest-rate years.
The 2022 Hoge Raad ruling
In December 2021, the Dutch Supreme Court (Hoge Raad) ruled that the existing Box 3 regime violated the European Convention on Human Rights' protection of property because it taxed gains that did not exist. The government was forced to scrap the old system and design a new one. The interim solution — applied from 2023 onward and adjusted for each year — is the "forfaitair vermogensrendement" with separate deemed returns for different asset categories.
The 2026 rules
For tax year 2026, Box 3 works as follows. Assets are divided into three categories: bank deposits (banktegoeden), other investments (overige beleggingen, including stocks, bonds, investment property, cryptocurrencies), and debts (schulden). Each category has a separate deemed return. For 2026 the rates are approximately 1.44 per cent for bank deposits, 6.04 per cent for other investments, and 2.62 per cent for debts (the debt rate is subtracted from the deemed return). These rates are recalculated annually based on market averages.
The deemed total return is then taxed at a single rate of 36 per cent in 2026. Importantly, there is a tax-free allowance (heffingsvrij vermogen) of €57,684 per person in 2026, doubled for couples filing jointly to €115,368. Below this threshold, no Box 3 tax is owed.
An example
Suppose a single expat has €40,000 in a savings account, €100,000 in a stock investment portfolio, and no Box 3-relevant debts at the end of 2025. Total assets: €140,000. Allowance: €57,684. Taxable basis: €82,316. The deemed return splits proportionally: €40,000 × 1.44% = €576 (savings), and €100,000 × 6.04% = €6,040 (investments). But only the portion above the allowance is taxed — so apply the proportional allowance: roughly 41 per cent of assets fall under the allowance, meaning roughly 41 per cent of the deemed return is exempt. Net taxable deemed return is approximately €3,910. Tax at 36 per cent: approximately €1,408. This is the Box 3 tax for the year.
The 30% ruling and Box 3
This is where the 30% ruling becomes hugely valuable for expats with foreign assets. Holders of the 30% ruling can elect to be treated as "partial non-resident taxpayers," which excludes all foreign-held Box 3 assets from the calculation. If you have a brokerage account in the US holding €500,000 of stock, partial non-resident status means that portfolio is not subject to Dutch Box 3 at all. For an expat with significant overseas wealth, this election can save tens of thousands of euros per year and is often the single most important reason to ensure the 30% ruling application is filed on time.
What counts as a Box 3 asset
The list is broad: bank balances, savings accounts, investment accounts (stocks, ETFs, bonds, mutual funds), cryptocurrencies, second homes (not your primary residence — that is in Box 1), loans receivable, and life insurance policies with a savings component. What does not count: your primary residence (Box 1), substantial business interests (Box 2), normal household possessions, art and collectibles for personal use, and pension assets that meet certain Dutch pension rules.
Reporting your assets
You report Box 3 assets on your annual income tax return based on their value at the start of the tax year (1 January). For Dutch bank accounts, the bank reports the year-end balance directly to the Belastingdienst — pre-filled on your return. For foreign accounts and investments, you must declare them yourself. The Belastingdienst increasingly receives data from foreign tax authorities under the Common Reporting Standard, so undeclared foreign assets are more likely to surface than they used to be.
The future
The government has committed to replacing the current interim system with a regime based on actual realised returns rather than deemed returns, originally targeted for 2027 but now delayed to 2028. Under the planned new regime, you would be taxed on actual gains: interest received, dividends, and realised capital gains. For most savers this would be slightly less harsh than the current deemed system; for active investors with high turnover it could be more administratively burdensome. The details remain in legislative discussion, and the original timetable has slipped multiple times — assume the 2026 interim rules apply for at least 2026 and 2027 returns.