https://github.com/uburuntu/exchequer
Privacy-first UK Capital Gains Tax Calculator Web App
https://github.com/uburuntu/exchequer
calculator capital gain tax uk
Last synced: 4 months ago
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Privacy-first UK Capital Gains Tax Calculator Web App
- Host: GitHub
- URL: https://github.com/uburuntu/exchequer
- Owner: uburuntu
- License: other
- Created: 2026-01-13T14:09:14.000Z (5 months ago)
- Default Branch: main
- Last Pushed: 2026-01-13T17:25:29.000Z (5 months ago)
- Last Synced: 2026-01-13T18:46:11.804Z (5 months ago)
- Topics: calculator, capital, gain, tax, uk
- Language: TypeScript
- Homepage:
- Size: 291 KB
- Stars: 0
- Watchers: 0
- Forks: 0
- Open Issues: 1
-
Metadata Files:
- Readme: README.md
- Contributing: CONTRIBUTING.md
- License: LICENSE
- Agents: AGENTS.md
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README
# Exchequer
**[exchequer.rmbk.me](https://exchequer.rmbk.me)**
A privacy-first, offline-capable browser application for calculating UK Capital Gains Tax. All calculations run entirely in your browser with zero data sent to servers.
## Features
**Broker Support**
- Charles Schwab, Trading 212, Morgan Stanley (MSSB), Sharesight, Vanguard, Freetrade
- RAW CSV format for custom imports
**HMRC Compliance**
- Same-Day Rule: Match same-day acquisitions and disposals
- Bed & Breakfast Rule: Match disposals with acquisitions within 30 days
- Section 104 Pooling: Average cost basis for remaining shares
**Transaction Types**
- Buy/Sell, Stock activity (RSU vesting, ESPP)
- Dividends, Interest income
- Stock splits, Spin-offs, Corporate actions
**Technical**
- Decimal precision with banker's rounding (matches HMRC requirements)
- Complete type safety with TypeScript strict mode
- British Heritage Editorial design aesthetic
## Quick Start
```bash
pnpm install
pnpm dev
```
Open [localhost:5174](http://localhost:5174) and upload your broker CSV files.
### Commands
| Command | Description |
|---------|-------------|
| `pnpm dev` | Start development server |
| `pnpm build` | Build for production |
| `pnpm test` | Run tests |
| `pnpm check` | Type check |
## Privacy & Security
- **Zero server communication** — all processing happens in your browser
- **No analytics or tracking** — no cookies, no external requests
- **Open source** — full source code available for audit
- **Offline capable** — works without internet connection
## Browser Compatibility
Chrome 90+, Firefox 88+, Safari 14+ (ES2020 support required)
## Credits
Inspired by [capital-gains-calculator](https://github.com/KapJI/capital-gains-calculator) by KapJI (MIT License).
## Contributing
See [CONTRIBUTING.md](CONTRIBUTING.md) for guidelines on adding new broker parsers and contributing to the project.
## Disclaimer
This calculator is provided for informational purposes only. Always consult with a qualified tax professional for advice specific to your circumstances. The developers make no warranty about the accuracy of calculations.
For HMRC guidance, see [gov.uk/capital-gains-tax](https://www.gov.uk/capital-gains-tax).
## License
[PolyForm Noncommercial License 1.0.0](LICENSE) — free for personal use, not for commercial purposes.