Know what stays. Anywhere.

OpenTax Atlas is an open-source, privacy-first calculator for comparing income tax, social contributions, business expenses and take-home income across fiscal regimes worldwide.

Live site: darkjoker360.github.io/opentax-atlas

The first release turns an Italian fiscal-regime comparison workbook into a reusable country-pack model:

• every sovereign country is selectable, plus independently modelled fiscal jurisdictions;
• Italy includes side-by-side forfettario and ordinary-regime scenarios;
• 16 additional jurisdictions include starter resident calculation packs;
• countries without a reviewed pack use an explicitly labelled, editable community template;
• all calculations run locally in the browser;
• every maintained pack carries a year, status, assumptions and a source link.

OpenTax Atlas provides educational estimates, not tax, legal or financial advice. Always verify the linked authority and consult a qualified professional before acting.

Requirements: Node.js 22.13 or newer.

npm install
npm run dev

The production checks are:

npm test
npm run build:pages

npm run build:pages creates the static out/ directory used by GitHub Pages.

Country packs live in lib/tax-data.ts. Calculation rules live in lib/tax-engine.ts.

Each pack declares:

• jurisdiction and currency;
• effective tax year;
• verified or estimate maintenance status;
• progressive tax bands or a country-specific regime model;
• social-contribution floors, rates and caps;
• source URL and modelling limitations.

The Italian pack reproduces the supplied workbook's practical comparison rows: gross revenue, taxable base, social contributions, income tax, effective burden, annual take-home and monthly take-home. It exposes the workbook's editable redditività coefficient (67% by default) and its first-five-tax-periods switch between the 5% and 15% substitute-tax rates. It uses the 2026 33% middle IRPEF rate and 2026 INPS contribution values.

Read CONTRIBUTING.md. A good country pull request includes an official primary source, an effective date, explicit assumptions and edge-case tests. Do not mark a pack verified when it relies only on an aggregator.

The workflow in .github/workflows/deploy-pages.yml builds and publishes the static site on every push to main.

The canonical repository is DarkJoker360/opentax-atlas. GitHub Pages serves it as a project site under /opentax-atlas.

Code is available under the MIT License. See NOTICE for third-party attribution. Tax authority publications and linked source data remain subject to their respective terms.