For optimizers
The return that reaches your account is the after-tax one
Which parcel is sold, how long it has been held and how much of the year's exemption is left all change the number. The simulators compute each of those effects from the rules rather than from a rule of thumb.
Per parcel, not per position
A position built over four years is four acquisition prices with four dates. Averaging them is where most spreadsheets quietly go wrong.
The holding clock
How long a parcel has been held can decide whether its gain is taxed at all. The simulator dates each parcel and names the rule it applied.
The yearly exempt amount
The exemption runs per year and is consumed by the gains already realised in it. The simulator tracks what is left rather than assuming a full allowance.
The tools, in a useful order
Everything is computed server-side by the same engine the paid product uses, and every figure arrives with its reasoning.
The rules in detail
The Reynders tax was not abolished: how it stacks with the capital gains tax
The Reynders tax — 30% on the interest component of funds holding more than 10% debt claims — was widely declared dead in 2025, but the law of 6 April 2026 kept it. How the two taxes combine, with a worked example following the circular.
3 Sept 2026
A worked example: a DEGIRO investor with €50,000 in a world ETF, 2024–2026
One fictional investor, one accumulating world ETF, followed from purchase through the 31 December 2025 step-up to a partial sale in 2026 — with the TOB, the step-up value and the 10% capital-gains tax shown line by line.
28 Aug 2026
You are on the opt-out side of the capital-gains tax: what lands on you
Under opt-out nobody withholds the 10% for you. Three jobs move from your broker to you — and one of them cannot be finished yet, because the declaration codes have not been published.
11 Aug 2026
The 31 December 2025 value, and why it usually helps you
For anything bought before 2026, your taxable gain starts from the last closing price of 2025 — not from what you paid.
2 Aug 2026
The ten-year exemption, and why it is measured per parcel
Gains on assets held continuously for at least ten years are exempt — a rule that turns each individual purchase into a record you need to keep.
11 Jun 2026
The €10,000 exemption is never automatic
Every Belgian taxpayer has an annual exemption on realized capital gains — but it exists only on the annual tax return, even when a broker already withheld 10%.
4 Jun 2026
The figure, and the reasoning behind it
The simulators publish their method and flag the rules that are still unsettled instead of rounding them away. A shared link replays exactly the same calculation.
Open the toolsFrequently asked questions
- Which parcel does a sale use?
- The cost-basis method is a rule parameter rather than a preference: the methodology page names the one applied and where it comes from.
- How is the yearly exemption applied?
- It is set against the year's realised gains, in the order the engine computes them, and the simulator shows the headroom left. Where the underlying rule is still disputed, the page says so rather than picking a side quietly.
- Does a long holding period change anything?
- The regime provides a long-holding exemption, expressed in years. The capital-gains simulator dates each parcel and states which rule its gain fell under.
- Does my broker withhold this?
- Some do, some do not, and some withhold at a rate that cannot be argued with. The tools list what each broker is reported to do and flag the cases where two of them contradict each other.
Not quite your situation?
The same tools, in the order that suits other ways of investing.