IMI Savings Simulator (Portugal)

A fully local, browser-only simulator for estimating IMI savings when submitting Modelo 1 do IMI, using a Caderneta Predial Urbana (PDF). No backend, no telemetry, and no external APIs.

Features

• 100% client-side (HTML/CSS/Vanilla JS)
• PDF parsing with a local PDF.js build (no CDN)
• Best-effort extraction + manual overrides
• Implements CIMI rules for VPT (round-up to next €10)
• Scenarios for baseline vs. Modelo 1 in current/next year

Quick start

python -m http.server

Then open: http://localhost:8000

Upload your Caderneta Predial Urbana PDF and review the parsed values.

Legal model (CIMI)

• VPT formula: Vt = Vc × A × Ca × Cl × Cq × Cv
• VPT rounding: always round up to the next €10
• Vc (2025/2026): valor médio de construção × 1.25
• Cv: based on building age at submission year
• Cq: 1 + majoratives − minoratives (Art. 43.º CIMI, Tabela I), clamped to [0.5, 1.7]
• A: computed from Aa/Ab with Caj tiers per CIMI

Cl (localização)

Use SIGIMI to confirm Cl: https://zonamentopf.portaldasfinancas.gov.pt/simulador/default.jsp

Privacy

• The PDF never leaves the browser
• No network calls once loaded
• No analytics or tracking
• Do not commit personal PDFs to the repo

Structure

• index.html
• style.css
• app.js
• libs/pdf.min.mjs
• libs/pdf.worker.min.mjs

Security notes

• No backend, no data persistence
• Runs fully offline after first load
• All dependencies are bundled locally

License

MIT License (see LICENSE).

Third-party

• PDF.js (Apache-2.0) — bundled locally in libs/