A full-stack invoice processing and tracking application powered by Mistral AI with automated VAT reliability checking for Czech businesses. Version 1.1.0 is pure Node.js application only.

• Mistral AI Integration: Uses mistral-small-latest model via Mistral API
• Integrated Backend: Single server combines backend API + Mistral proxy (port 3002)
• Separate Database: Uses mistral_invoices.db (SQLite database)
• Extraction of financial data: Intensively tested System prompt guarantees to get the best from Mistral Small 3.2
• ISDOC import: You can import ISDOC e-invoices
• VAT payer reliability check: Native Node.js SOAP client for direct check with MF database of unreliable VAT payers
• Financial Analytic: Analytics of VAT for VAT return statements on quarterly basis (could be easily modified for monthly period), supplier analysis by date range

• Files: mistral_server.js, mistral_database.js, Mistral_Invoice_processor.html, package.json
• Database: mistral_invoices.db
• API: Mistral with mistral-small-latest model (the newest version of Mistral Small 3.2 )
• Tabs: Invoice Extractor, Expense Tracker, Suppliers

Web based application (html file) runs on localhost port 3002

Before installation, ensure you have:

• Node.js (version 14 or higher) - Download here
• npm (comes with Node.js)
• Mistral API Key - Get one here

# Check Node.js version
node --version

# Check npm version
npm --version

Note for v1.0.0 users: Python and vat_checker.py are no longer required. VAT checking is now natively integrated into Node.js. Simply run npm install to get the new fast-xml-parser dependency.

Copy all necessary files to chosen directory (mistral_server.js, mistral_database.js, package.json, mistral_invoices.db)

npm install

This will install all required Node.js packages including:

• express - Web server framework
• sqlite3 - Database driver
• fast-xml-parser - XML parsing for VAT SOAP API
• node-fetch - HTTP client
• Other dependencies (cors, helmet, body-parser)

When you first open Mistral_Invoice_processor.html:

1. Navigate to the "Invoice Extractor" tab
2. Enter your Mistral API key in the API Configuration section
3. Optionally enable password protection for the key
4. Click "Save API Key"

The API key is stored encrypted in your browser's localStorage and is never sent anywhere except to Mistral API via the integrated proxy.

From the project directory:

npm start

You should see output like:

🚀 Mistral Invoice Manager Server starting...
Connected to Mistral SQLite database: mistral_invoices.db
Mistral database tables initialized successfully
✅ Mistral Invoice Manager Server running on port 3002
Frontend available at: http://localhost:3002
API available at: http://localhost:3002/api
Mistral Proxy available at: http://localhost:3002/api/mistral/chat
📝 Model: mistral-small-latest with T=0.1, top_p=0.95
💾 Database: mistral_invoices.db

Open Mistral_Invoice_processor.html directly in your browser:

1. Upload an invoice (PDF, PNG, JPG, JPEG, GIF, WEBP)
2. Upload an ISDOC file (ISDOC XML format)
3. Review extracted data - Mistral AI automatically extracts invoice fields
4. VAT reliability check - System automatically checks VAT status
5. Edit as needed - All fields are editable
6. Download JSON or Add to Tracker

1. View statistics by quarter and year
2. Upload existing JSON files for bulk import
3. Filter by quarter to see period-specific data
4. Export data as CSV for reporting
5. View supplier breakdown with pie chart and table

1. Select date range - Choose start and end dates
2. Click Load Data - Fetches invoices from database
3. View statistics:
   • Total Expenditures (including VAT)
   • Total Suppliers
   • Total Invoices
4. Analyze suppliers:
   • Pie chart (suppliers with ≥2% of total)
   • All Suppliers table with share on you wallet (%) and number of invoices

The SQLite database file is created automatically at same directory.

You can directly edit the database using:

• DB Browser for SQLite - Download here
• DBeaver - Download here
• Any SQLite client

Simply open the mistral_invoices.db file to view and edit records.

To backup your data:

cp mistral_invoices.db mistral_invoices_backup_$(date +%Y%m%d).db

or export data directly from database

Issue: Port 3002 is already in use

Solution: :

• Change the port in mistral_server.js: const PORT = 3000-5000;
• And update Mistral_Invoice_processor.html: const API_BASE_URL = 'http://localhost:300x/api';

Issue: API errors or authentication failures

Solution:

• Verify Mistral API key is correct
• Check you have credits in your Mistral account
• Check browser console (F12) for specific error messages
• Ensure the server is running on same port as frontend html application

Possible causes:

• Incorrect VAT number format (system automatically strips non-digits)
• MF CR (Financial Directorate) API service is temporarily down
• Network connectivity issues
• SOAP service timeout (30 seconds)

Solutions:

• Verify the VAT number is correct
• Check server logs for detailed error messages
• Manually set the VAT reliability status if automatic check fails
• Wait a few minutes and try again if service is temporarily unavailable

The Mistral backend provides these REST API endpoints:

• POST /api/mistral/chat - Process invoice extraction with Mistral AI

• GET /api/health - Server health check
• GET /api/invoices - Get all invoices
• POST /api/invoices - Add new invoice
• GET /api/invoices/quarter/:quarter/year/:year - Get invoices by quarter
• PUT /api/invoices/:id - Update invoice
• DELETE /api/invoices/:id - Delete invoice
• DELETE /api/invoices - Clear all invoices
• GET /api/stats?quarter=X&year=Y - Get statistics
• GET /api/suppliers?quarter=X&year=Y - Get supplier stats
• GET /api/suppliers/daterange?startDate=YYYY-MM-DD&endDate=YYYY-MM-DD - Get suppliers by date range
• POST /api/check-vat - Check VAT reliability

Mistral_Faktury/
├── package.json                        # Application dependencies
├── mistral_server.js                   # Backend server + Mistral proxy + VAT checker (port 3002)
├── mistral_database.js                 # Database operations
├── Mistral_Invoice_processor.html      # Frontend application
├── mistral_invoices.db                 # SQLite database (auto-created)
└── README.md                           # This file

1. API Keys: Mistral API keys are stored encrypted in browser localStorage
2. Database: SQLite database has no authentication - suitable for single-user or trusted network use
3. VAT Service: Connects to official Czech tax authority API (MFCR)
4. Local Storage: Invoice data persists in database, not browser storage
5. Proxy: Integrated proxy prevents CORS issues when calling Mistral API

• RAM: Minimum 2GB
• Disk Space: 100MB + space for database
• Network: Required for AI extraction and VAT checking
• Browser: Modern browser (Chrome, Firefox, Safari, Edge)

• Node.js Documentation: https://nodejs.org/docs/
• SQLite Documentation: https://www.sqlite.org/docs.html
• Express Documentation: https://expressjs.com/
• Mistral AI Documentation: https://docs.mistral.ai/
• Mistral API Console: https://console.mistral.ai/

This application is provided as-is for personal and commercial use.

Last Updated: October 2025 Version: 1.1.0 - Native Node.js VAT checker (removed Python dependency)