GST Invoice

About the Project

GST Invoice is a desktop ERP application designed specifically for the construction industry in India. The application handles end-to-end GST-compliant invoicing, inventory management, billing workflows, and financial reporting tailored to construction project accounting.

India's GST (Goods and Services Tax) system has specific rules for the construction industry, including Input Tax Credit (ITC) on materials, reverse charge mechanisms for sub-contractor payments, and project-based billing. This application was built to handle all these complexities.

Key Features

• GST-compliant invoice generation with CGST, SGST, and IGST breakdown
• Construction material inventory management with stock tracking
• Project-based billing with milestone tracking and progress invoices
• Sub-contractor payment management with reverse charge mechanism
• Input Tax Credit (ITC) calculation and reconciliation
• Financial reporting — P&L, balance sheets, cash flow for construction projects
• PDF invoice export with customizable company letterhead
• Multi-project management dashboard
• Client management with payment history and outstanding tracking
• GST return filing data export (GSTR-1, GSTR-3B compatible formats)

Technical Architecture

The application was built as a desktop app using C# and .NET for the backend business logic and data layer, with a React/Next.js frontend rendered within an Electron-style desktop shell. MySQL served as the local database.

This architecture allowed for a modern, web-like UI experience (React) while maintaining the reliability and offline capability of a desktop application. The C# layer handled all business logic, GST calculations, and database operations via a local API.

Challenges

• Implementing accurate GST calculation logic across all construction-specific scenarios
• Designing the MySQL schema to handle complex project-based accounting relationships
• Ensuring the React UI remained responsive with large datasets (hundreds of invoices)
• Building reliable PDF generation for legally compliant GST invoices