How the Norway mva (vat) calculator is verified

Inputs

Input	Field	Type
Amount (NOK)	`amount`	number
Direction	`direction`	string
What is being supplied	`category`	string
No VAT charged by you: zero-rated export, or the customer accounts for the tax	`reverseCharge`	boolean
Charitable or non-profit institution or organisation	`charity`	boolean
Taxable turnover in a twelve-month period	`turnover12Months`	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)
Rate for the category	`rate`	`category = 'food' ? $const.foodRate : category = 'services12' ? $const.servicesRate : category = 'marine' ? $const.marineRate : $const.standardRate`
Rate applied	`effectiveRate`	`reverseCharge ? 0 : rate`
Net	`netAmount`	`direction = 'remove' ? $round(amount / (1 + effectiveRate), 2) : $round(amount, 2)`
VAT (MVA)	`vatAmount`	`$round(netAmount * effectiveRate, 2)`
Gross	`grossAmount`	`$round(netAmount + vatAmount, 2)`
Registration limit	`registrationThresholdApplied`	`charity ? $const.registrationThresholdCharity : $const.registrationThreshold`
Must register for VAT	`mustRegister`	`turnover12Months > registrationThresholdApplied`

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
`standardRate`	0.25
`foodRate`	0.15
`servicesRate`	0.12
`marineRate`	0.1111
`registrationThreshold`	50000
`registrationThresholdCharity`	140000

Test vectors (6)

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 — N1 1,000 kr net at 25%

given `amount`	1000
given `direction`	add
given `category`	standard
given `reverseCharge`	no
given `charity`	no
given `turnover12Months`	0
expect `vatAmount`	250
expect `grossAmount`	1250
expect `netAmount`	1000

Case 2 — N2 1,250 kr gross back to net

given `amount`	1250
given `direction`	remove
given `category`	standard
given `reverseCharge`	no
given `charity`	no
given `turnover12Months`	0
expect `netAmount`	1000
expect `vatAmount`	250

Case 3 — N3 food at 15%

given `amount`	1000
given `direction`	add
given `category`	food
given `reverseCharge`	no
given `charity`	no
given `turnover12Months`	0
expect `vatAmount`	150
expect `grossAmount`	1150

Case 4 — N4 a hotel room at 12% — not the 8% the 2014 resolution stated

given `amount`	1000
given `direction`	add
given `category`	services12
given `reverseCharge`	no
given `charity`	no
given `turnover12Months`	0
expect `rate`	0.12
expect `vatAmount`	120

Case 5 — N5 exactly 50,000 kr does not yet require registration

given `amount`	0
given `direction`	add
given `category`	standard
given `reverseCharge`	no
given `charity`	no
given `turnover12Months`	50000
expect `mustRegister`	false

Case 6 — N6 a charity at 100,000 kr is still under its 140,000 kr limit

given `amount`	0
given `direction`	add
given `category`	standard
given `reverseCharge`	no
given `charity`	yes
given `turnover12Months`	100000
expect `registrationThresholdApplied`	140000
expect `mustRegister`	false

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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