How the Brazil ipva calculator is verified

Inputs

Input	Field	Type
Valor FIPE (BRL)	`fipeValue`	number
Estado (UF)	`state`	string
Alíquota se 'Outro' (fração, ex. 0.03)	`customRate`	number
Idade do veículo (anos)	`ageYears`	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)
Alíquota aplicada	`stateRate`	`($s := state; $s = 'SP' ? $const.rateSP : $s = 'RJ' ? $const.rateRJ : $s = 'MG' ? $const.rateMG : $s = 'SC' ? $const.rateSC : $s = 'PR' ? $const.ratePR : customRate)`
Exempt	`exempt`	`ageYears > $const.ageExemption ? 1 : 0`
IPVA anual	`ipva`	`$round(exempt = 1 ? 0 : fipeValue * stateRate, 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
`ageExemption`	20
`rateSP`	0.04
`rateRJ`	0.04
`rateMG`	0.04
`rateSC`	0.02
`ratePR`	0.019

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 — C1 SP, FIPE R$80,000, 3-year-old car

given `fipeValue`	80000
given `state`	SP
given `ageYears`	3
expect `stateRate`	0.04
expect `exempt`	0
expect `ipva`	3200

Case 2 — C2 same car registered in Paraná — the 2026 rate cut

given `fipeValue`	80000
given `state`	PR
given `ageYears`	3
expect `stateRate`	0.019
expect `ipva`	1520

Case 3 — C3 22-year-old car — age exemption

given `fipeValue`	30000
given `state`	SP
given `ageYears`	22
expect `exempt`	1
expect `ipva`	0

Sources

Sefaz-SP — IPVA · checked 2026-08-04
Sefaz-SC — calendário IPVA 2026 · checked 2026-08-04
Tabela FIPE · checked 2026-08-04

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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