Box 3 explained: how the Dutch tax your savings, investments and UK ISAs

Back home the taxman taxes the interest you actually earn. In the Netherlands, Box 3 taxes a return the government assumes you made on everything you own on 1 January, and that includes your UK savings and your ISA.

The short version

• Dutch income tax is split into three boxes. Box 3 covers savings, investments, second homes and other wealth, worldwide, valued on 1 January [1].
• For 2026 each person gets a tax-free allowance of EUR 59,357 (about £49,460). Above that, savings are deemed to earn 1.28% (provisional), investments and other assets 6.00%, and debts cost 2.70%. The deemed return is taxed at 36% [1].
• The Supreme Court (Hoge Raad) ruled in 2021 and again in 2024 that taxing a fictional return can breach your rights. Since 1 July 2025 you can prove a lower actual return under the Wet tegenbewijsregeling box 3 [3][4].
• A tax on actual returns is planned, but the government only "aims" for 1 January 2028 and it isn't law yet [4].
• The Dutch ignore the ISA wrapper: an ISA is just savings or shares in Box 3. You can keep it but can't pay in once you're non-resident in the UK [6].

Pound conversions use the Bank of England spot rate of 5 November 2026 (£1 = EUR 1.2002).

How the three boxes work

If you've only ever had PAYE in Britain, the Dutch return looks odd at first. Your income is sorted into three boxes, each with its own rules:

Your own home sits in Box 1, not Box 3, with its mortgage interest relief. Everything else you own, from a Nationwide savings account to a flat in Leeds, goes into Box 3 once you're a Dutch tax resident. The Netherlands taxes residents on worldwide income and assets, so "it's in the UK" is not an exemption.

The 2026 numbers

The Belastingdienst (the Dutch tax office) sets three deemed return rates each year. The 2026 figures are below, alongside 2025 for comparison [1][2].

The savings and debt rates for 2026 are provisional; the tax office says it will fix them early in 2027 [1]. Fiscal partners can share a double allowance of EUR 118,714 (about £98,910).

How the sum works

1. Add up your bank balances, investments and other assets on 1 January, and your debts above the EUR 3,800 threshold.
2. Apply the deemed rates to each category to get a total deemed return.
3. Turn that into an average percentage of your total net assets.
4. Take off the tax-free allowance and apply that percentage to what's left.
5. Pay 36% of the result [1].

A few worked examples for a single person in 2026, on our sums using the official rates:

The second line is where it stings. Deemed at 6%, an index fund that had a flat year still costs you real money. Which is exactly what the courts objected to.

What the courts changed

The system has been in the dock for years. In the Kerstarrest of December 2021, the Hoge Raad ruled that taxing a fixed, fictional return was discriminatory, and taxpayers who'd paid too much got money back. In June 2024 it ruled that the replacement fictional system discriminated too, which led to more refunds [4]. On 25 June 2026, though, the court ruled that people who hadn't objected for 2017 to 2020 have no right to a refund for those years [4]. If you're new to the Netherlands, the lesson is simple: if you think a Box 3 assessment is wrong, object in time.

The counter-evidence rule

The Wet tegenbewijsregeling box 3 lets you show that your actual return was lower than the deemed one. It has applied since 1 July 2025 and stays until the new system arrives [4]. From the 2025 tax year you report your actual return in your normal tax return; for 2024 and earlier you use the form Opgaaf werkelijk rendement [3].

Actual return means interest, dividends and rent, plus changes in value over the year, rises and falls, including gains you haven't cashed in. If the total is negative it counts as zero, and a loss can't be carried forward. There's no tax-free allowance on this route and most costs can't be deducted. You're not obliged to use it, and the tax office uses whichever figure, deemed or actual, is better for you [3].

For savers with modest interest, the deemed 1.28% is often close to reality. For investors, a bad market year is when the counter-evidence route pays.

The new system

The cabinet has said for years that it wants to tax actual returns, and the government's own page says it "aims" to bring that in on 1 January 2028 [4]. It isn't law yet, and Dutch press reports in autumn 2026 suggested it could slip further. Until it changes, the deemed system with the counter-evidence rule applies. Treat anything you read about "the new Box 3" as proposed until both houses of parliament have voted.

UK accounts, ISAs and property

UK savings and investments

Interest on your UK bank accounts goes into Box 3 like any Dutch account. Under the 2008 UK–Netherlands double taxation convention, interest is taxable only in the country where you live [5], so once you're Dutch resident and have left the UK system properly, HMRC shouldn't be taxing it. Our guide to the Statutory Residence Test explains when that is.

Your ISA

The ISA is a UK tax wrapper and the Dutch don't recognise it. A cash ISA counts as bank savings, and a stocks and shares ISA counts as investments at the 6% deemed rate. GOV.UK confirms you can keep an ISA open after you move abroad and keep the UK tax relief on what's already in it, but you can't add money while you're non-resident, and you must tell your provider [6]. In other words, the ISA still shelters you from UK tax, which matters if you come home, but it doesn't shelter you from Box 3. Our guide to ISAs when you move abroad has more.

A UK buy-to-let

A rented-out flat in Britain sits in Box 3 at its value, less any mortgage. The UK keeps the first right to tax the rent [5], so you stay in the Non-Resident Landlord Scheme and file a UK return. The convention then requires the Netherlands to give relief by reducing its tax on that item [5]. You still list the property on your Dutch return; the relief is worked out there. See UK income while you live abroad.

Pensions are not Box 3

UK workplace and personal pensions you haven't drawn generally stay outside Box 3, and pensions in payment are Box 1 income. Under the convention, UK private pensions paid to a Dutch resident are generally taxable only in the Netherlands, with limited exceptions [5]. Never move a UK pension into an overseas scheme to dodge Dutch tax without regulated financial advice; our guide to pension transfer warnings explains why.

Practical tips for the first years

• The year you arrive. Box 3 looks at 1 January. If you weren't yet resident on that date, your worldwide savings generally aren't in Box 3 for that year, but check your first return carefully, because the rules for part-year residents have quirks.
• Keep year-end statements. For the counter-evidence route you need values on 1 January and 31 December, plus income received, for every account. UK banks and platforms will happily email you annual statements; file them.
• The 30% ruling. People on the 30% ruling used to be able to opt out of Box 3 on most foreign assets. That option has been wound down, so don't rely on older advice from colleagues. Our guide to the 30% ruling covers what's left.
• Get help when it's complicated. A tax adviser who knows both countries can check your situation, especially if you hold a UK rental, a stake in a company or crypto.

Box 3 comes up every spring in our community group for Brits in the Netherlands, usually when someone opens their first Dutch tax return and finds their ISA on it.

Sources

1. Belastingdienst: Berekening box 3-inkomen 2026
2. Belastingdienst: Berekening box 3-inkomen 2025
3. Belastingdienst: Wat is mijn werkelijk rendement?
4. Rijksoverheid: Box 3
5. GOV.UK (HMRC): 2008 UK–Netherlands Double Taxation Convention as amended by the 2013 Protocol
6. GOV.UK: Individual Savings Accounts, if you move abroad
7. KVK: Starten als ondernemer? Alles over belastingen en btw (updated 27 October 2026)

Keep reading

• Dutch taxes for Brits: the UK link and your State Pension
• The 30% ruling for Brits
• ISAs when you move abroad
• Double taxation agreements and reliefs