This project provides an AI coding agent plugin and skill package designed to automate Japanese tax filing (確定申告) for individuals and small businesses. It offers end-to-end support, from bookkeeping and generating financial statements to automatically inputting data into the e-Tax system, significantly streamlining the tax declaration process for users.

How It Works

The system operates as an AI coding agent plugin, adhering to the SKILL.md open standard, enabling compatibility with over 40 AI agents including Claude Code, Cursor, GitHub Copilot, and Gemini CLI. It processes user-provided financial data, including OCR-based ingestion of receipts and invoices, performs bookkeeping using double-entry accounting, calculates income and consumption taxes, and automates the final submission via e-Tax. This integrated approach aims to reduce manual effort and potential errors in tax preparation.

Quick Start & Requirements

• Installation: Install via uv tool install git+https://github.com/kazukinagata/shinkoku for CLI usage, or use agent-specific commands like /plugin install shinkoku@shinkoku for Claude Code or npx skills add kazukinagata/shinkoku for the Skills CLI.
• Prerequisites: Python 3.11 or higher, uv package manager. Browser automation tools (Claude in Chrome, Antigravity Browser Sub-Agent, or Playwright CLI) are required for e-Tax interaction.
• Setup: Run /setup in your working directory for interactive configuration, .gitignore setup, and database initialization.
• Documentation: Links to specific agent setup instructions are provided within the README.

Highlighted Details

• Broad AI Agent Compatibility: Supports over 40 AI coding agents through the SKILL.md standard.
• End-to-End Automation: Covers bookkeeping, tax calculation (income/consumption), and e-Tax input.
• OCR & Multi-modal Support: Ingests receipts, invoices, withholding slips, etc., via OCR. Supports multi-modal LLMs and offers dual-verification via sub-agents on compatible platforms.
• Comprehensive Tax Scenarios: Handles sole proprietors (blue/general), employees with side income, consumption tax payers (various methods), Furusato納税, housing loan credits, medical expenses, and cryptocurrency income.

Maintenance & Community

The project welcomes contributions via Issues and Pull Requests. Specific details regarding active maintainers, sponsorships, or dedicated community channels (like Discord/Slack) are not explicitly detailed in the README.

Licensing & Compatibility

The project is released under the MIT License, which permits broad use, modification, and distribution, including for commercial purposes and integration into closed-source applications.

Limitations & Caveats

The tool does not support specific tax categories such as stock investment income (separate taxation), FX trading gains, real estate income, retirement income, capital gains from property sales, foreign tax credits, agricultural/forestry/mountain income, or non-residents. It exclusively supports blue tax returns. A strong disclaimer states that tax filing is the user's responsibility, and developers are not liable for any damages. The tool is based on the Reiwa 7 (2025 tax year) tax system, and users must verify all generated outputs.