Calculation principles
SENNA Finance uses standard financial-mathematics relationships implemented in a shared, versioned JavaScript engine. Public calculator inputs and outputs are processed locally in the browser.
Validation workflow
- Define inputs, units, boundaries, and formula.
- Create normal, zero-rate, edge, and invalid-input test cases.
- Compare results with an independent calculation or authoritative example.
- Review page explanation, assumptions, warnings, and rounding.
- Publish a formula-engine version and review date.
Rounding
The engine calculates with JavaScript numeric precision. Most currency and percentage values are rounded to two decimal places for display. Schedules preserve underlying values until export.
Formula versions
Current public engine: v1.1.0. Formula changes are documented in the repository changelog. A changed formula should trigger new test cases and a new version.
Regulated calculations
APR, tax, payroll, insurance, and regulatory definitions can differ by country. A global educational estimate is labeled accordingly; a country-specific tool must identify jurisdiction, effective date, official source, and limitations.
Corrections
Reports should include tool URL, exact inputs, actual result, expected result, and supporting source. Submit them through the correction form.