Open Pajak

Open Pajak is a fully client-side tax calculator for the Indonesian tax regime. The SPA bundles calculators for PPh 21/26, PPh 22, PPh 23, PPh Final Pasal 4(2), PPN, and PPNBM, and turns every calculation into a transparent table + formula narrative so practitioners can audit each step. All inputs stay in the browser—no personal identifiers (NIK, names, addresses) are ever collected or stored.

• Multi-tax coverage: switch between /pph21, /pph22, /pph23, /pph4-2, /ppn, and /ppnbm via the TanStack Router powered AppShell navigation.
• Domain-specific forms: each route renders a TaxPageLayout with tailored inputs (subject types, PTKP, TER category, DPP overrides, inclusive/exclusive PPN mode, dsb) plus sample presets to help users learn the flows.
• Calculation transparency: pure functions in src/lib/tax/*.ts emit breakdown rows that surface DPP, PKP, tariff tiers, and rounding for every scenario. FormulaExplanationCard and FormulaSourceNote reference the official Buku PPh 21/26 guidance (public/Buku_PPh2126_Release_20240108.pdf).
• Shared UI primitives: form fields, number formatting, cards, tables, and alerts live in src/components/** for consistent styling with Tailwind + shadcn/ui tokens.
• Offline-first SPA: built with React 19, Vite, and Bun. No backend, so the bundle can be deployed to static hosting (Cloudflare Pages, Netlify, dsb.).

open-pajak/
├─ README.md                # This file
├─ open-pajak-v1/           # Bun + Vite workspace
│  ├─ src/
│  │  ├─ components/        # AppShell, tax layout primitives, shadcn wrappers
│  │  ├─ lib/tax/           # Pure calculators per tax type
│  │  └─ routes/            # File-based TanStack Router pages (one per tax calculator)
│  ├─ public/               # Static assets (favicon, Buku PPh reference PDF)
│  ├─ bun.lock / package.json / tsconfig.json
│  └─ vite.config.ts        # Vite + TanStack router plugin + Tailwind setup
└─ ...                      # Local planning docs (kept outside version control)

ℹ️ Only README.md is intended for upstream pushes; other docs stay local for planning/reference.

All app code lives inside open-pajak-v1/. Use Bun (>= 1.1) for dependency management and scripts.

cd open-pajak-v1
bun install

# Local development (Vite dev server on port 3000)
bun dev

# Production bundle + type check
bun run build

# Preview the built assets
bun run serve

• bun test — run the Vitest suite (React Testing Library is available for DOM assertions).
• bun run lint — TypeScript-aware ESLint (TanStack config) for catching logic mistakes.
• bun run format — Prettier format check.
• bun run check — Convenience script (format write + eslint --fix) when sweeping the repo.

Add new tests next to their pages/engines (e.g., src/routes/pph21/pph21.page.test.tsx or src/lib/tax/pph21.test.ts) and focus on edge cases like TER rounding, PTKP thresholds, PKP zero floors, PPN inclusive pricing, etc.

1. Model the math first inside src/lib/tax/<tax>.ts. Keep every helper pure/deterministic and follow the interfaces in src/lib/tax/types.ts.
2. Update the UI inside src/routes/<tax-type>.tsx, using shared primitives such as TaxFormSection, TaxResultTable, and TaxSummaryCard.
3. Document formulas with FormulaExplanationCard and source links so users can trace regulations back to Buku PPh / PMK references.
4. Respect privacy: inputs must remain numeric or enumerated metadata; never prompt for or persist personal identifiers.

• The build is a static bundle; host it on any CDN/static host.
• Static assets live in open-pajak-v1/public/. Only keep essentials (favicon + PDF reference); unused template files have been removed.
• If you need environment toggles, use import.meta.env, but prefer committed constants whenever possible.

This project is provided as-is for educational and operational use in calculating Indonesian taxes. Consult professional tax advisors before relying on the outputs for filings.