A result should come with its working

Our calculation contract

Every deterministic tool has a pure calculation function. It does not read the DOM, call a network, write to storage or depend on a browser event. The form is only a way to collect and validate input; the result can be tested independently.

What appears beside a result

• A plain-language explanation of the inputs.
• The formula used, without asking an AI model to do arithmetic.
• A worked example with independently expected values.
• Effective period, source references, last-verified date and reviewer status.
• Limitations, privacy behavior and a direct correction route.

Rounding and testing

Money calculations use decimal-safe arithmetic and document their rounding boundary. Unit tests cover normal, invalid and boundary cases; integration tests cover forms; browser checks cover discovery, accessibility and mobile layouts. Static worked examples use independently expected values so a live calculation cannot silently validate itself.

Privacy and update process

Current calculations, QR payloads and documents stay in the browser. Analytics accepts only a small event allowlist and excludes entered values, identities and document contents. Business economics offers an explicit, tab-only scenario handoff that imports matching fields only after confirmation; it is not persistent storage or cloud sync. Regulatory material is stored in a reusable effective-dated policy package, reviewed against named sources and updated through code review rather than scraped into a result at runtime.

Lifecycle and release controls

Tool definitions can be internal, beta, live, stale-disabled or retired. Internal and disabled tools do not enter search or the sitemap. A feature flag can hold a route out of the public directory, while a stale policy can replace the interface with a noindex explanation instead of continuing to calculate from outdated rules.

Review and corrections

Formula changes are intended to be reviewed as code and content together. If you find a result that looks wrong, use the report link with the tool name and version. Do not send private amounts or business details in a report.

GST Calculator policy

GST is treated as controlled policy data, not a timeless rate constant. The GST Calculator displays policy version gst-general-rates-2025-09-22-v1, its effective date, last verification date and official source links. Only the 5% and 18% headline presets are exposed; they are choices for arithmetic, not product or service classification.

Exclusive mode calculates GST on the entered taxable value. Inclusive mode extracts the GST component from the entered total. Currency values use decimal arithmetic and half-up rounding at two decimal places. Intra-state components reconcile as CGST plus SGST/UTGST; inter-state tax is shown as IGST; the tool never infers place of supply.

Review the detailed GST methodology, policy-version model and source-verification summary before relying on a result.