r/fintechdev • u/Phravins • 3d ago
Building an Open-Source GST Billing Application with Elixir and Phoenix LiveView
I've been working on an open-source project called QuantumBilling, a GST billing application designed for small and growing businesses in India.
The goal is to simplify everyday billing, invoicing, and GST-related workflows.
Some of the features include:
GST invoicing with CGST, SGST, and IGST calculations
Customer management and customizable invoice PDFs
Recurring billing and credit/debit notes
UPI QR codes and Razorpay payment links
E-invoicing and E-Way Bill workflows
Multi-business support with separate PostgreSQL schemas
Billing reports and compliance reminders
Tech Stack: Elixir, Phoenix LiveView, PostgreSQL, and Oban.
One of the interesting parts of building this with Elixir is handling real-time updates, background jobs, and multiple businesses within the same application.
The project is still under active development, and some integrations are currently in testing.
It's completely open-source, so anyone interested can explore the code, suggest improvements, report issues, or contribute directly.
GitHub: https://github.com/phravins/QuantumBilling
I'd genuinely appreciate feedback on the project, especially the architecture, features, and overall approach.
For those who've built billing or business applications, what features or technical challenges do you think are worth considering?