Best Invoice Generator – Dual Interface Python Application for GST Billing

Invoice Generator

So I made this Invoice Generator using Python. It’s a pretty handy tool that helps you make GST invoices, and you can use it either on your computer or through a website. It’s mainly made for Indian businesses that need proper tax stuff and downloadable invoice files.It can calculate taxes on its own, makes clean PDF invoices with QR codes, and even lets you add your company’s branding. The best part is, it works offline, so your data stays private and you don’t have to rely on any outside services.

Overview

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Key Features

Desktop GUI (Tkinter)

• Simple interface for entering invoice data.
• Add unlimited items with:
  • Description
  • HSN Code
  • Quantity
  • Rate
  • GST %
• Automatically calculates:
  • Subtotal
  • CGST
  • SGST
  • Grand Total
• Generates professional-grade PDF invoices using ReportLab.
• Embeds a machine-readable QR code with invoice details.
• Offline usage—no internet required.

Web App (Flask)

• Responsive HTML interface with structured templates.
• Accepts the same invoice parameters as the desktop version.
• PDF invoices generated on-the-fly and available for download.
• Uses the same logic and database structure as the desktop app.
• Custom branding support via logo file.

Technical Highlights

• Built using Python 3.8+.
• Tkinter powers the desktop graphical interface.
• Flask framework enables the web version.
• ReportLab used for generating styled PDF documents.
• QR code generation for digital invoice metadata.
• Local data stored in SQLite (invoices.db).
• Clean file organization with modular structure.

Project Structure

INVOICE-GENERATOR-main/
│
├── invoice-app/               # Flask web application
│   ├── app.py                 # Main application logic
│   ├── templates/             # HTML templates for web pages
│   │   └── index.html         # Invoice input form
│   ├── static/                # Static files (logo, styles)
│   └── requirements.txt       # Python dependencies for web app
│
├── invoice_generator.py       # Tkinter desktop application
├── instance/
│   └── invoices.db            # SQLite database
├── logo.png             # Logo for branding

Available Features

• Dual interface (Tkinter for desktop, Flask for web)
• GST-compliant invoice layout
• Automatic calculation of SGST and CGST
• Support for multiple invoice items per bill
• QR code embedding into each invoice PDF
• Offline PDF generation
• SQLite database for invoice storage
• Local branding with customizable logo
• No external dependencies beyond Python packages
• Minimalist, easy-to-use user interfaces

Installation & Setup

Prerequisites

• Python 3.8 or later installed
• pip (Python package manager)

Setup Instructions

1. Extract the ZIP File
   • Unzip the downloaded folder to your desired location.
2. Set Up a Virtual Environment (Recommended) python -m venv venv source venv/bin/activate # On Windows: venv\Scripts\activate
3. Install Dependencies
   Navigate to the invoice-app folder and install required packages: pip install -r requirements.txt
4. Run the Web Interface
   Inside the invoice-app folder: python app.py Open your browser and go to: http://localhost:5000
5. Run the Desktop Interface
   From the root folder: python invoice_generator.py

Configuration

You can customize the application to fit your business needs:

• Logo: Replace Bosch Logo.png with your own image.
• Company Info: Edit the PDF template or fields in the GUI.
• GST Rates: Enter appropriate GST percentages at runtime.
• Database: The SQLite file (invoices.db) will store your records securely.

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