How the Netherlands Nettoloon (net salary) calculator is verified
Inputs
| Input | Field | Type |
|---|---|---|
| Bruto jaarloon | grossAnnual | 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) |
|---|---|---|
| Box 1 belasting | box1Tax | ($g := grossAnnual; $round((($g < $const.band1 ? $g : $const.band1) * $const.rate1) + (($g > $const.band1 ? (($g < $const.band2 ? $g : $const.band2) - $const.band1) : 0) * $const.rate2) + (($g > $const.band2 ? ($g - $const.band2) : 0) * $const.rate3), 2)) |
| Algemene heffingskorting | ahk | (grossAnnual <= 29736 ? 3115 : ($h := 3115 - 0.06398 * (grossAnnual - 29736); $round($h > 0 ? $h : 0, 2))) |
| Arbeidskorting | arbeidskorting | ($g := grossAnnual; $a := $g <= 11965 ? 0.08324 * $g : $g <= 25845 ? 996 + 0.31009 * ($g - 11965) : $g <= 45592 ? 5300 + 0.0195 * ($g - 25845) : 5685 - 0.0651 * ($g - 45592); $round($a > 0 ? $a : 0, 2)) |
| Belasting | tax | ($x := box1Tax - ahk - arbeidskorting; $round($x > 0 ? $x : 0, 2)) |
| Netto / jaar | netAnnual | $round(grossAnnual - tax, 2) |
| Netto / maand | netMonthly | $round(netAnnual / 12, 2) |
Rates and thresholds
The expressions above read these as $const. They are the figures the annual refresh replaces, so they live as data rather than being written into the formulas — which is what makes a year-on-year change a one-line diff instead of an edit to arithmetic.
| Constant | Value |
|---|---|
band1 | 38883 |
band2 | 78426 |
rate1 | 0.3575 |
rate2 | 0.3756 |
rate3 | 0.495 |
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 — S1 40,000 EUR
given grossAnnual | 40000 |
|---|---|
expect box1Tax | 14320.22 |
expect ahk | 2458.31 |
expect arbeidskorting | 5576.02 |
expect tax | 6285.89 |
expect netAnnual | 33714.11 |
Case 2 — S3 120,000 EUR — credits fully phased out
given grossAnnual | 120000 |
|---|---|
expect box1Tax | 49332.15 |
expect ahk | 0 |
Sources
- Belastingdienst — tarieven box 1 (2026) · checked 2026-10-17
- Belastingdienst — tabel algemene heffingskorting 2026 · checked 2026-10-17
- Belastingdienst — tabel arbeidskorting 2026 · checked 2026-10-17
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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