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How the Hungary áfa (vat) calculator is verified

Inputs

InputFieldType
Amountamountnumber
Directiondirectionstring
What is being suppliedcategorystring
Turnover this yearannualTurnovernumber
B2B reverse charge appliesreverseChargeboolean
Turnover last yearpriorYearTurnovernumber

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 valueFieldFormula (JSONata)
Rateratecategory = 'reduced1' ? $const.reducedRate1 : category = 'reduced2' ? $const.reducedRate2 : category = 'zero' ? $const.zeroRate : $const.standardRate
Effective RateeffectiveRatereverseCharge ? 0 : rate
Net AmountnetAmountdirection = 'remove' ? $round(amount / (1 + effectiveRate), 2) : $round(amount, 2)
Vat AmountvatAmount$round(netAmount * effectiveRate, 2)
Gross AmountgrossAmount$round(netAmount + vatAmount, 2)
Must RegistermustRegisterpriorYearTurnover > $const.registrationThreshold or annualTurnover > $const.registrationThreshold

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.

ConstantValue
standardRate0.27
reducedRate10.05
reducedRate20.18
zeroRate0
registrationThreshold18000000

Test vectors (7)

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 10000 HUF net at the standard rate

given amount10000
given directionadd
given categorystandard
given reverseChargeno
given annualTurnover0
given priorYearTurnover0
expect vatAmount2700
expect grossAmount12700
expect netAmount10000

Case 2 — S2 12700 HUF gross back to net at the standard rate

given amount12700
given directionremove
given categorystandard
given reverseChargeno
given annualTurnover0
given priorYearTurnover0
expect netAmount10000
expect vatAmount2700

Case 3 — S3 10000 HUF net at the 5% rate

given amount10000
given directionadd
given categoryreduced1
given reverseChargeno
given annualTurnover0
given priorYearTurnover0
expect vatAmount500
expect grossAmount10500

Case 4 — S4 10000 HUF net at the 18% rate

given amount10000
given directionadd
given categoryreduced2
given reverseChargeno
given annualTurnover0
given priorYearTurnover0
expect vatAmount1800
expect grossAmount11800

Case 5 — S5 a zero-rated daily newspaper: a rate of nil

given amount10000
given directionadd
given categoryzero
given reverseChargeno
given annualTurnover0
given priorYearTurnover0
expect vatAmount0
expect grossAmount10000

Case 6 — S6 either year over 18 million HUF ends the exemption

given amount100
given directionadd
given categorystandard
given reverseChargeno
given annualTurnover1000000
given priorYearTurnover20000000
expect mustRegistertrue

Case 7 — S7 both years under the limit

given amount100
given directionadd
given categorystandard
given reverseChargeno
given annualTurnover10000000
given priorYearTurnover10000000
expect mustRegisterfalse

Sources

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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