Methodology · AU-BIZ-001
GST Calculator
Add GST, remove GST or split a GST-inclusive amount using the current Australian GST rate, with full working shown and sources cited.
Engines and formulas
- E20 · Business arithmetic engine
GST arithmetic per §13.18 with explicit rounding levels and largest-remainder allocation so invoice lines always reconcile to totals.
Registered formulas: F-GST-001 · F-GST-002
Rule packs
Statutory values come only from versioned, hash-verified rule packs citing official sources. Current status of the packs this calculator can use:
- au-gst-standardactive · v0.1.0
Verification
Engines carry boundary tests at every bracket edge, property-based tests, reconciliation invariants and, where official worked examples exist, tests that reproduce them exactly. The full source register is on the sources page.