Mistral Invoice & Receipt Manager - Installation Guide

A full-stack invoice processing and tracking application powered by Mistral AI with automated VAT reliability checking for Czech businesses. Version 1.2.0 is pure Node.js fully separated Frontend/Backend application.

Features

• 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

2. **Packages **

• Files: mistral_server.js, mistral_database.js, index.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 (index.html file in Public directory) runs on localhost port 3002

http://localhost:3002

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Prerequisites

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 if already installed:

# Check Node.js version
node --version

# Check npm version
npm --version

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Installation Steps

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.

1. Navigate to Project Directory

Copy all necessary files and Public folder to chosen directory (mistral_server.js, mistral_database.js, package.json) or simply

git clone https://github.com/PetrAPConsulting/Invoice-processor.git
cd invoice-processor

2. Install Dependencies

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)

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Running the Mistral Application

Start the Mistral Server

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
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

Access the Application

Open browser and insert:

http://localhost:3002

Mistral API Key Setup

When you first open app on

http://localhost:3002

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.

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Using the Mistral Application

Tab 1: Invoice Extractor

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

Tab 2: Expense 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

Tab 3: Suppliers

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

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Database Management

Mistral Database Location

The SQLite database file is created automatically at same directory.

Direct Access

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.

Backup

To backup your data:

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

or export data directly from database

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Troubleshooting

Server Won't Start

Issue: Port 3002 is already in use

Solution: :

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

Mistral API Issues

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

VAT Checking Not Working

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

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API Endpoints

The Mistral backend provides these REST API endpoints:

Mistral Proxy

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

Database Operations

• 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

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File Structure

YourAppFolder/
├── mistral_server.js
├── mistral_database.js
├── mistral_invoices.db      ← SQLite database (created automatically)
├── package.json
├── public/                  ← All frontend files go here
│   ├── index.html
│   └── Assets/
│       └── favicon.png
│       └── images.png
└── node_modules/            ← Installed

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Security Notes

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

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System Requirements

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

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Support and Resources

• 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/

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License

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

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Last Updated: December 2025 Version: 1.2.0 - Native Node.js