How DeGiro investments fit into Box 3
Investments you hold at DeGiro count as "overige bezittingen" (other assets) in Box 3, the Dutch tax on wealth. What's taxed is not your profit — it's an assumed ("forfaitair") return the tax office applies to the value of your portfolio on one date a year: 1 January, the peildatum.
That means two investors with identical portfolios pay the same Box 3 tax even if one made 40% and the other lost money — the tax is on the assumed return, not the real one. A separate reform, taxing actual return, is planned for 2028.
Which DeGiro value to report
Report the total value of your DeGiro investments on 1 January of the tax year, converted to euros. This is the market value of all your positions plus any uninvested cash in the account on that date — not an average over the year, and not the value when you file.
DeGiro publishes this for you. The annual statement (jaaroverzicht) under Activity shows your portfolio value on 1 January, which is the figure the Belastingdienst expects. If you also hold cash at the broker, include it.
How the tax is calculated (2023 onward)
For a DeGiro-only portfolio the math collapses to one line: (value − heffingsvrij vermogen) × fictive return × tax rate. The heffingsvrij vermogen is the tax-free slice; only wealth above it is taxed. The fictive return for investments and the tax rate are set each year.
For 2025 the numbers are: heffingsvrij vermogen €57,684 per person, fictive return on investments 5.88%, and a tax rate of 36%. FolioInsights ships the official rates for 2023, 2024 and 2025 and uses the latest published set for later years until new ones are announced.
A worked example
Say your DeGiro portfolio is worth €100,000 on 1 January 2025 and you file as a single person. Subtract the tax-free slice: €100,000 − €57,684 = €42,316 of taxable wealth. Apply the 5.88% fictive return: €42,316 × 5.88% = €2,488 of assumed income.
Tax that assumed income at 36%: €2,488 × 36% ≈ €896. So a €100,000 DeGiro portfolio costs roughly €896 in Box 3 tax for 2025 — regardless of whether the portfolio actually rose or fell that year.
How FolioInsights estimates your Box 3
FolioInsights reconstructs your portfolio value on each 1 January from your imported DeGiro CSV, then applies the same official rates above to estimate the Box 3 tax year by year. It's an estimate to help you plan — not a tax filing — and the Belastingdienst's own figure is always the authoritative one.
Because everything is computed in your browser from your own CSV, your holdings never leave your device to produce the estimate. The estimator covers tax year 2023 onward; the pre-2023 "vermogensmix" model used a different formula and is out of scope.
Which DeGiro value do I report in Box 3?
The total value of your DeGiro investments — plus any cash in the account — on 1 January of the tax year, in euros. This single date is called the peildatum. It is not an average over the year and not the value on the day you file your return.
Where do I find that value on DeGiro?
DeGiro's annual statement (jaaroverzicht), available under Activity in the web platform, lists your portfolio value on 1 January. That's the number the Belastingdienst expects. You can also read it from your own records if you exported an account.csv around that date.
Are my actual gains and dividends taxed in Box 3?
No. Box 3 taxes a fictive (assumed) return on your wealth, not your real profit. Your actual dividends and capital gains are not directly taxed under the current system, which is why a strong year and a weak year produce the same Box 3 bill. This changes with the planned 2028 actual-return reform.
What is the tegenbewijsregeling?
After the Hoge Raad rulings on Box 3, you can submit a "counter-proof" (tegenbewijs) if your actual return for the year was lower than the fictive return. You then pay tax on the lower, real figure. Keeping a clear record of your true return — which a tracker makes easy — is what makes that claim possible.
Does FolioInsights file or calculate my official tax?
No. FolioInsights gives an estimate to help you plan and sanity-check, computed in your browser from your DeGiro CSV. It is not tax advice and does not file anything. The Belastingdienst's calculation is the authoritative one; for your specific situation, consult a tax advisor.