How the China 增值税 (VAT) calculator is verified

Inputs

Input	Field	Type
Amount (CNY)	`amount`	number
This amount is	`direction`	string
What is being sold	`category`	string
Annual taxable sales (CNY)	`annualTurnover`	number
Monthly sales (CNY) — small-scale taxpayers	`monthlySales`	number
Overseas seller — the Chinese buyer withholds the VAT	`reverseCharge`	boolean

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	`rate`	`category = 'reduced1' ? $const.reducedRate1 : (category = 'reduced2' ? $const.reducedRate2 : (category = 'zero' ? $const.zeroRate : (category = 'simplified' ? $const.simplifiedRate : (category = 'smallScale' ? $const.smallScaleReducedRate : $const.standardRate))))`
Effective Rate	`effectiveRate`	`reverseCharge or belowThreshold ? 0 : rate`
Net	`netAmount`	`direction = 'remove' ? $round(amount / (1 + effectiveRate), 2) : $round(amount, 2)`
VAT charged by the seller	`vatAmount`	`$round(netAmount * effectiveRate, 2)`
Gross	`grossAmount`	`$round(netAmount + vatAmount, 2)`
Must Register	`mustRegister`	`annualTurnover > $const.registrationThreshold`
Below Threshold	`belowThreshold`	`category = 'smallScale' and $n(monthlySales) < $const.monthlyThreshold`
VAT withheld and remitted by the buyer	`withheldVat`	`reverseCharge ? $round(netAmount * rate, 2) : 0`

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`	0.13
`reducedRate1`	0.09
`reducedRate2`	0.06
`zeroRate`	0
`simplifiedRate`	0.03
`smallScaleReducedRate`	0.01
`registrationThreshold`	5000000
`monthlyThreshold`	100000

Test vectors (12)

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 — V1 1,000 yuan of goods at 13%

given `amount`	1000
given `direction`	add
given `category`	standard
given `reverseCharge`	no
given `annualTurnover`	0
given `monthlySales`	100000
expect `vatAmount`	130
expect `grossAmount`	1130
expect `netAmount`	1000

Case 2 — V2 1,130 yuan gross back to net at 13%

given `amount`	1130
given `direction`	remove
given `category`	standard
given `reverseCharge`	no
given `annualTurnover`	0
given `monthlySales`	100000
expect `netAmount`	1000
expect `vatAmount`	130

Case 3 — V3 construction at 9%

given `amount`	1000
given `direction`	add
given `category`	reduced1
given `reverseCharge`	no
given `annualTurnover`	0
given `monthlySales`	100000
expect `vatAmount`	90
expect `grossAmount`	1090

Case 4 — V4 consulting at 6%

given `amount`	1000
given `direction`	add
given `category`	reduced2
given `reverseCharge`	no
given `annualTurnover`	0
given `monthlySales`	100000
expect `vatAmount`	60
expect `grossAmount`	1060

Case 5 — V5 small-scale taxpayer at the 2026 1% rate

given `amount`	1000
given `direction`	add
given `category`	smallScale
given `reverseCharge`	no
given `annualTurnover`	0
given `monthlySales`	100000
expect `vatAmount`	10
expect `grossAmount`	1010

Case 6 — V6 exported goods are zero-rated

given `amount`	1000
given `direction`	add
given `category`	zero
given `reverseCharge`	no
given `annualTurnover`	0
given `monthlySales`	100000
expect `vatAmount`	0
expect `grossAmount`	1000

Case 7 — V7 3% simplified levy rate

given `amount`	1000
given `direction`	add
given `category`	simplified
given `reverseCharge`	no
given `annualTurnover`	0
given `monthlySales`	100000
expect `vatAmount`	30

Case 8 — V8 overseas seller: the buyer withholds 130 at the rate; the seller charges none

given `amount`	1000
given `direction`	add
given `category`	standard
given `reverseCharge`	yes
given `annualTurnover`	0
given `monthlySales`	100000
expect `vatAmount`	0
expect `grossAmount`	1000
expect `withheldVat`	130

Case 9 — V9 exactly 5 million yuan is still small-scale (“未超过五百万元”)

given `amount`	100
given `direction`	add
given `category`	standard
given `reverseCharge`	no
given `annualTurnover`	5000000
given `monthlySales`	100000
expect `mustRegister`	false

Case 10 — V10 above 5 million yuan: general taxpayer

given `amount`	100
given `direction`	add
given `category`	standard
given `reverseCharge`	no
given `annualTurnover`	6000000
given `monthlySales`	100000
expect `mustRegister`	true

Case 11 — V11 small-scale, monthly sales of 99,999 do not reach the threshold (“未达到起征点”): no VAT

given `amount`	1000
given `direction`	add
given `category`	smallScale
given `reverseCharge`	no
given `annualTurnover`	0
given `monthlySales`	99999
expect `belowThreshold`	true
expect `vatAmount`	0
expect `grossAmount`	1000

Case 12 — V12 small-scale, monthly sales of exactly 100,000 reach it: 1% on the whole amount

given `amount`	1000
given `direction`	add
given `category`	smallScale
given `reverseCharge`	no
given `annualTurnover`	0
given `monthlySales`	100000
expect `belowThreshold`	false
expect `vatAmount`	10
expect `grossAmount`	1010

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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