How the Belgium indépendant calculator is verified
Inputs
| Input | Field | Type |
|---|---|---|
| Annual net taxable income (EUR) | annualIncome | 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) |
|---|---|---|
| Social contributions | socialContributions | ($i := annualIncome; $round($const.rate1 * $min([$i, $const.ceiling1]) + $const.rate2 * $max([0, $min([$i, $const.ceiling2]) - $const.ceiling1]), 2)) |
| Taxable Income | taxableIncome | $round($max([0, annualIncome - socialContributions - $const.exemptAmount]), 2) |
| Income tax (IPP) | incomeTax | ($t := taxableIncome; $round($const.r1 * $min([$t, $const.b1]) + $const.r2 * $max([0, $min([$t, $const.b2]) - $const.b1]) + $const.r3 * $max([0, $min([$t, $const.b3]) - $const.b2]) + $const.r4 * $max([0, $t - $const.b3]), 2)) |
| Net income / year | netIncome | $round($max([0, annualIncome - socialContributions - incomeTax]), 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 |
|---|---|
ceiling1 | 75024.54 |
ceiling2 | 110562.42 |
rate1 | 0.205 |
rate2 | 0.1416 |
exemptAmount | 11180 |
b1 | 16320 |
b2 | 28800 |
b3 | 49840 |
r1 | 0.25 |
r2 | 0.4 |
r3 | 0.45 |
r4 | 0.5 |
Test vectors (3)
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 — 50,000 EUR net taxable income — a typical full-time indépendant
given annualIncome | 50000 |
|---|---|
expect socialContributions | 10250 |
expect taxableIncome | 28570 |
expect incomeTax | 8980 |
expect netIncome | 30770 |
Case 2 — 20,000 EUR — part-time
given annualIncome | 20000 |
|---|---|
expect socialContributions | 4100 |
expect taxableIncome | 4720 |
expect incomeTax | 1180 |
expect netIncome | 14720 |
Case 3 — 130,000 EUR — above the second contribution ceiling
given annualIncome | 130000 |
|---|---|
expect socialContributions | 20412.19 |
expect taxableIncome | 98407.81 |
expect incomeTax | 42823.9 |
expect netIncome | 66763.91 |
Sources
- INASTI — Combien de cotisations sociales dois-je payer ? · checked 2026-08-22
- Cotisations indépendant Belgique 2026 : taux 20,5% / 14,16% et plafonds · checked 2026-08-22
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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