The three boxes, in one paragraph
Dutch income tax sorts your income into three boxes. Box 1 is work, pension and your own home (see income tax and filing). Box 2 is a substantial shareholding of 5% or more in a company. Box 3 is everything else you own: savings, investments, crypto, a second home, a home abroad, minus your debts. Each box has its own rules and rates, and box 3 is the one that catches internationals off guard.
How box 3 is calculated in 2026
- Count what you owned on 1 January 2026 (peildatum), anywhere in the world: bank balances, shares, funds, crypto, a second home, a home abroad at market value. Not counted: the home you live in and its mortgage (box 1), pension capital and annuity (lijfrente) capital, and green investments up to €26,715 per person.
- Subtract debts, except the first €3,800 per person (€7,600 for fiscal partners), which is ignored. A mortgage on a home abroad is a box 3 debt. Your Dutch home mortgage is not, it belongs in box 1.
- Take off the tax-free allowance (heffingsvrij vermogen): €59,357 per person, €118,714 for fiscal partners. Below that, box 3 is zero.
- Apply the deemed returns to your actual mix: 1.28% on bank savings (provisional), 6.00% on investments and property, minus 2.70% on the counted debt (provisional). The result is scaled to the part of your wealth above the allowance.
- Tax the deemed return at 36%.
A worked example. Single, €40,000 in savings and €50,000 in an index fund on 1 January 2026. Total €90,000, of which €30,643 is above the allowance. The deemed return on the mix is about 3.9% (savings at 1.28%, fund at 6%), so €1,196 counts as income. Tax: 36% of €1,196, about €430.
Had the whole €90,000 been in a savings account, the tax would be about €141. Had it all been in the fund, about €662. The mix matters more than the total.
Try your own numbers in the box 3 calculator. It shows every line above separately.
A home abroad
The most common box 3 question from internationals, and the answer has two halves.
It counts and must be declared. A home abroad, whether you use it during holidays, rent it out or leave it empty, is a box 3 asset at its market value. The mortgage on it is a box 3 debt. It uses up part of your tax-free allowance, and it must appear in your Dutch return.
But with a treaty, the Dutch tax on it is relieved. The Netherlands has tax treaties with about 100 countries, including Spain, Portugal, Italy, France, Germany, Poland, the UK, the US, India, Turkey, Morocco, Brazil, China and South Africa. Treaties give the right to tax real estate to the country where it stands. The Netherlands then grants relief (aftrek ter voorkoming van dubbele belasting): the share of your box 3 tax attributable to the property is deducted, usually bringing it to zero. What remains is the box 3 tax on your other assets, calculated as if the property had used part of the allowance.
- Rental income is not taxed separately in the Netherlands, because box 3 taxes a deemed return, not the rent. The other country usually does tax rent from non-residents. Spain, for example, has a non-resident income tax with its own filing. Check the local rules.
- Without a treaty (a small minority of countries), the property is simply taxed in box 3 like any other asset. The calculator has a switch for this.
The 30% ruling and box 3
Ruling holders whose ruling started before 2024 can still opt, in 2025 and 2026, to be treated as non-resident for box 3 and leave all foreign assets out of the return. This partial foreign tax liability ends for everyone on 1 January 2027. If that is you, 1 January 2027 is the first reference date on which your savings, investments and property abroad count in full. Read more in the 30% ruling explained.
If your real return was lower: counter-evidence
After court rulings, the Belastingdienst must let you prove a lower actual return. The tegenbewijsregeling works like this: you report your actual return via the Opgaaf werkelijk rendement. Actual return means interest, dividends, rent and all value changes, realised or not, and costs are not deductible. If the actual return is lower than the deemed return, you pay tax on the actual return instead. The catch is that the tax-free allowance then no longer applies. So it only helps when the real return was clearly low, for example a year in which your investments fell. It is available for 2021 onwards.
What is changing
- 2027. Partial foreign tax liability for ruling holders disappears. The green investments exemption drops to €200.
- 2028. A new system taxing actual returns (Wet werkelijk rendement box 3) is planned to start on 1 January 2028. In September 2026 it was still before the Senate. Until it passes, the deemed-return method above applies.
- The savings and debt percentages for 2026 are provisional and are set definitively early in 2027, before returns are filed.
Practical points
- 1 January is a snapshot. Money in a bank on that day counts. A large purchase in late December lowers your base. A bonus paid on 2 January instead of 30 December does too. This is legal and everyone does it.
- Fiscal partners can split the joint box 3 base between them in the return however they like. It rarely changes the total, but it can when one partner has other income that affects credits.
- Foreign bank accounts are visible. The Netherlands exchanges account data automatically with about 100 countries. Declare everything.
- Crypto is an "other asset" at 6.00% deemed return, wherever the exchange or wallet is.
Questions people ask
Is box 3 a tax on my actual interest and gains?
No. It assumes a deemed return on what you owned on 1 January and taxes that at 36%. If your real return was lower you can use the counter-evidence scheme, but then the tax-free allowance no longer applies.
Do I need to declare a bank account abroad?
Yes. Box 3 covers worldwide assets. The only exception until the end of 2026 is a 30% ruling holder whose ruling started before 2024 and who opts for partial foreign tax liability.
My partner and I are not married. Are we fiscal partners?
You are if you are registered at the same address and meet one extra condition, such as a notarial cohabitation contract, a child together, a joint home or a joint pension registration. Fiscal partners have a joint allowance of €118,714.
When does the new system start?
The plan is 1 January 2028. It was still before the Senate in September 2026. Until then the deemed-return method applies.
Coaching and education, not regulated advice. Your own return and the Belastingdienst's assessment are the source of truth for your case.