How the Belgium verkeersbelasting calculator is verified
Inputs
| Input | Field | Type |
|---|---|---|
| CO₂ (g/km) | co2 | number |
The formula
Each derived value below is computed by the Valem engine from the expression shown, in this order. Nothing else runs — there is no hidden code path.
| Derived value | Field | Formula (JSONata) |
|---|---|---|
| Jaarlijkse belasting | tax | ($c := co2; $round($c = 0 ? 0 : $c <= 120 ? 280 : $c <= 160 ? 550 : $c <= 200 ? 900 : 1400, 2)) |
Test vectors (2)
Every case is executed against this model on each build, by the Java engine and independently by a JavaScript one. A mismatch of a single cent fails the build, so the page cannot ship advertising a figure the model no longer produces.
Case 1 — C1 120 g/km
given co2 | 120 |
|---|---|
expect tax | 280 |
Case 2 — C2 160 g/km
given co2 | 160 |
|---|---|
expect tax | 550 |
Sources
- Verkeersbelasting Vlaanderen · checked 2026-08-02
Check it yourself — and reuse it
The whole model as JSON — inputs, outputs, formulas, vectors and sources in one re-runnable document.
This model is published under CC BY 4.0: use it, adapt it, build on it, with attribution. The licence covers the model — the expression of each rule and the arrangement of the catalog. The rates and thresholds are law, and nobody licenses those; the sources above are where they come from.
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