Box 3 for real estate in 2026: the new rules of the game

Box 3 is the Dutch wealth-tax box. If you own rental property in the Netherlands, this is the box that taxes its value, even if you are based abroad. This article walks through how it works in 2026.

What changed in 2026?

For years Box 3 was a black box for real-estate investors. Since the Supreme Court ruling of 6 June 2024 you may declare your actual return when the flat-rate return turns out to be higher than what you really earned. In 2026 this principle is being further worked out in policy.

How is real estate taxed now?

Rental property sits in Box 3 under "other assets". The mechanics roughly look like this:

Worked example (simplified)

Suppose: a property with a WOZ valuation of € 300,000, a € 150,000 mortgage, no other Box 3 wealth, no tax partner.

1. Asset: € 300,000 → flat-rate return at 6% = € 18,000
2. Debt (after threshold): € 150,000 → flat-rate return at 2.70% = € 4,050
3. Net return: € 18,000 − € 4,050 = € 13,950
4. Taxable base after exemption: the Tax Office allocates this with a proportional formula, not by simply subtracting the exemption from the return
5. Tax = 36% on the allocated taxable base

Flat-rate versus actual return

The Supreme Court said: if your actual return is demonstrably lower than the flat rate, you may declare that.

What counts as actual return?

Do include:

• Rental income (base rent)
• Mortgage interest on a Box 3 debt
• Appreciation or depreciation of the property in that year
• An own-use charge if you use the property (partly) yourself - 5.06% of the WOZ valuation pro-rated by the number of days of use

Do not (just) include:

• Service costs - these are pass-through expenses, not return
• Maintenance costs of a second home are in principle not deductible when computing actual return (with limited exceptions, such as deferred maintenance at purchase - always have this checked)
• Management fees from an external letting agent are often not deductible as a cost - verify per case

Own use from 2026

Do you have a second home you use yourself (a holiday home, pied-à-terre, family-care property)? Then under the actual-return regime you must add an own-use charge. The Tax Office typically uses 5.06% of the WOZ valuation × (days of use ÷ 365) as the economic rental value, unless you can demonstrate a higher actual rent.

For purely let property without any own use, this charge does not apply.

What to do in 2026

1. Inventory per property: WOZ valuation, mortgage debt, mortgage interest, rental income, service costs (separately), maintenance, vacancy periods, and any own use in days.
2. Compute the flat-rate return at portfolio level with the final 2026 percentages.
3. Compute your actual return at portfolio level (including value changes and any own use).
4. Choose the cheaper path in your tax return - remember the choice applies to the entire Box 3 wealth.
5. Keep your evidence for at least 7 years: invoices, contracts, payment statements, valuations, maintenance bills.

Common mistakes

Four traps:

• Forgetting appreciation when computing actual return - value increases count even if you haven't sold
• Deducting maintenance on a second home when in principle it isn't deductible at actual return
• Missing mortgage interest if part of the debt still falls under Box 1
• Cherry-picking per property - actual return applies to your whole Box 3 wealth

Conclusion

Box 3 for real estate in 2026 demands more administration, but it also gives you more control once you can credibly show that your actual return is lower than the flat rate. The difference is in the details: the debt flat rate, the debt threshold, own use, and the precise scope of what does and does not count as a cost.

With a dashboard like Propty you record per property the rental income, service costs, maintenance and mortgage interest separately - so your accountant can quickly run both scenarios at year end.

Also read how to set up iDEAL payments so your incoming payments line up cleanly, or schedule a short demo to see how Propty prepares the data your accountant needs.