Box 3 calculator — Dutch wealth tax on an ETF portfolio
Box 3 does not tax what your portfolio earned. It taxes what the law assumes it earned, and then charges you whether or not the assumption held. That single design choice is why a Dutch investor can owe tax in a year the market fell, and why the honest way to think about Box 3 is not as a tax on gains at all but as an annual charge on the holding — the same shape as a fund's ongoing charge, and usually much larger than one.
The calculator
How it works
Assets are valued on 1 January, the tax-free threshold is subtracted from the total, and what remains is split between the savings and investment categories in proportion to their share of the whole portfolio — not savings first. Each slice earns its own deemed return, 1.28% for savings and 6.00% for investments in 2026, and the two are added and taxed at 36%. For a portfolio held entirely in ETFs that works out at 2.16% of the taxable amount every year. The drag shown by the calculator is measured against your whole portfolio rather than the taxable part, so it starts below that ceiling and climbs toward it as the exempt tranche shrinks relative to the total.
What it assumes
The projection holds the 2026 rates flat for every future year, which they will not be — the rates are reset annually and two of the four years on offer here are still provisional. It models one person's securities only: debts, a second home, green investments and the deductions that go with them are all outside it, and so is the counter-evidence route introduced in 2025, under which you can elect to be taxed on your actual return when that is lower than the deemed one. A loss-making year is precisely when that election matters and precisely what this page does not compute for you. The threshold of €59,357 per person, €118,714 with a fiscal partner, is applied in full.
The background, in prose
ETF tax in the Netherlands — how Box 3 actually works explains the rules this calculator applies, why they are shaped the way they are, and what they mean for choosing a fund.
Common questions
- Do I still pay Box 3 in a year my portfolio fell?
- Yes, and this is the feature of the system people find hardest to believe. The assessment is made on the value of your assets on 1 January and the return is deemed, so a portfolio that lost twenty percent over the year is taxed exactly as if it had earned the deemed rate. Set the gross return slider to zero and the calculator still shows a bill; the share-of-gains figure goes to infinity because you are dividing a real tax by a gain that never happened.
- Does the tax-free threshold shelter my investments first?
- No, and assuming it does will overstate the exemption. The threshold comes off your total assets, and the taxable remainder is then divided between savings and investments in the same proportions as the portfolio itself. Someone holding half cash and half ETFs gets half the exemption applied against each, so the investment slice is taxed at 6.00% on its full pro-rata share rather than being sheltered by cash sitting alongside it.
- How much does a fiscal partner actually save?
- It doubles the threshold to €118,714, so the saving is the tax on the extra €59,357 of sheltered assets — at the 2026 investment rate, roughly €1,282 a year for a portfolio comfortably above the joint threshold. The calculator computes your own figure and shows it as a separate note, because the saving is capped: once both thresholds are consumed, filing jointly changes nothing.