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
0.2
reducedRate1
0.05
zeroRate
0
registrationThreshold
90000
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 — S1 100.00 GBP net at the standard rate
given amount
100
given direction
add
given category
standard
given reverseCharge
no
given annualTurnover
0
expect vatAmount
20
expect grossAmount
120
expect netAmount
100
Case 2 — S2 120.00 GBP gross back to net at the standard rate
given amount
120
given direction
remove
given category
standard
given reverseCharge
no
given annualTurnover
0
expect netAmount
100
expect vatAmount
20
Case 3 — S3 100.00 GBP net at the reduced rate
given amount
100
given direction
add
given category
reduced1
given reverseCharge
no
given annualTurnover
0
expect vatAmount
5
expect grossAmount
105
Case 4 — S4 zero-rated: a rate of nil, not an exemption
given amount
100
given direction
add
given category
zero
given reverseCharge
no
given annualTurnover
0
expect vatAmount
0
expect grossAmount
100
Case 5 — S5 rolling turnover over 90,000 forces registration
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.