How the Australia registration calculator is verified
Inputs
| Input | Field | Type |
|---|---|---|
| Tare weight (kg) | tareWeight | 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) |
|---|---|---|
| Weight Component | weightComponent | $round(tareWeight * $const.perKg, 2) |
| Annual rego | total | $round($const.baseFee + $const.ctp + weightComponent, 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 |
|---|---|
baseFee | 85 |
ctp | 450 |
perKg | 0.35 |
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 NSW 1,400 kg
given tareWeight | 1400 |
|---|---|
expect weightComponent | 490 |
expect total | 1025 |
Case 2 — C2 1,600 kg
given tareWeight | 1600 |
|---|---|
expect weightComponent | 560 |
expect total | 1095 |
Sources
- Service NSW rego · 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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