Shipped project
PaymentCalcs
PaymentCalcs is a suite of 30 deterministic calculators for Australian money decisions — income tax and take-home pay, PAYG withholding, stamp duty for every state and territory, loan amortisation, savings and GST. Fantom Labs designed and built the product and its calculation engine.
Context
PaymentCalcs is a suite of 30 deterministic calculators for Australian money decisions — income tax and take-home pay, PAYG withholding, stamp duty for every state and territory, loan amortisation, savings and GST. Fantom Labs designed and built the product and its calculation engine.
Australians comparing tax, duty and loan outcomes need numbers they can trust, but most online calculators hide their assumptions and quietly go stale when statutory rates change.
Approach
- Every result shows its working — formulas, intermediate values, assumptions, sources and limitations alongside the answer.
- Statutory rates and thresholds ship as versioned, hash-verified rule packs citing the ATO, RBA and state revenue offices.
- Pure integer-cent arithmetic runs entirely client-side with no accounts or tracking, and a calculator halts rather than estimating if its rule pack cannot load.
Scope
- Product design
- Web application
- Calculation engine
- Versioned rule packs
See it live
This is a real, shipped project. Visit paymentcalcs.com.au to see it in production.