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
0.15
registrationThreshold
60000
Test vectors (5)
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 100.00 NZD net at 15%
given amount
100
given direction
add
given reverseCharge
no
given annualTurnover
0
expect vatAmount
15
expect grossAmount
115
expect netAmount
100
Case 2 — S2 115.00 NZD gross back to net (IR375 worked example)
given amount
115
given direction
remove
given reverseCharge
no
given annualTurnover
0
expect netAmount
100
expect vatAmount
15
Case 3 — S3 reverse charge: the supplier charges no GST
given amount
100
given direction
add
given reverseCharge
yes
given annualTurnover
0
expect vatAmount
0
expect grossAmount
100
Case 4 — S4 turnover over 60 000 NZD: registration required
given amount
100
given direction
add
given reverseCharge
no
given annualTurnover
70000
expect mustRegister
true
Case 5 — S5 turnover under the threshold: voluntary only
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.