Billing software shouldn't be a black box.

Over the past few months, I've been building something in the open, and I'd love to share it with this group.

QuantumBilling

An open-source billing app for Indian businesses:

• GST invoices & templates
• Credit/debit notes
• E-way bills
• Recurring billing & payment links
• Reports & compliance reminders
• Tech stack:* Elixir, Phoenix LiveView, PostgreSQL, Oban
• A small fact worth knowing*

WhatsApp, the app you're reading this on, runs on *Erlang*. One WhatsApp server handled 2 million connections.
Discord runs on *Elixir* and handles *12 million+ users at once* with a team of just *5 engineers*.

Both run on the same engine, the BEAM. Its secret:

1. Millions of tiny isolated processes
2. If one crashes, it restarts automatically and nothing else breaks

QuantumBilling is built on that same engine.

Areas open for contribution

• E-invoice & e-way bill integrations
• HSN code finder
• UI improvements in LiveView
• Tests & docs
• GST domain knowledge from CAs and tax professionals

If you've been curious about Elixir, this could be a good real-world project to explore.

https://github.com/phravins/QuantumBilling

Feedback, ideas, and contributions are all welcome.