Invoice API – Open-source invoicing that doesn't suck

Maxence Londot — Wed, 29 Apr 2026 19:52:01 +0000

Why another invoicing tool?

Every freelancer and SaaS founder needs invoices. Yet most solutions are either bloated SaaS subscriptions or clunky Excel templates.

Invoice API is different – it's a lightweight, self-hosted REST API that generates professional PDF invoices in under 5 seconds. Built with FastAPI, WeasyPrint, and Stripe, it gives you full control without vendor lock-in.

What can it do?

Create customers & invoices via a clean REST API
Generate PDF invoices with a single GET request (WeasyPrint, ~30KB per PDF)
Receive Stripe webhooks for real-time payment status updates
Dashboard to see all invoices at a glance
Docker-Compose one-liner – docker compose up -d and you're live

Tech stack

Layer	Technology
API	FastAPI + Pydantic v2
Database	PostgreSQL 16
Cache	Redis 7
PDF Engine	WeasyPrint 62
Payments	Stripe API (webhook)
Container	Docker + Docker Compose
Auth	Bearer JWT tokens

Quick start

# Clone & start
git clone https://github.com/UniTy/invoice-api.git
cd invoice-api
docker compose up -d

# Create a customer
curl -X POST http://localhost:8000/api/v1/customers \
  -H "Content-Type: application/json" \
  -d '{"name":"Acme Corp","email":"billing@acme.com"}'

# Create an invoice
curl -X POST http://localhost:8000/api/v1/invoices \
  -H "Content-Type: application/json" \
  -d '{"customer_id":1,"items":[{"desc":"Consulting","qty":10,"price":150}],"currency":"eur"}'

# Download PDF
curl http://localhost:8000/api/v1/invoices/1/pdf -o invoice-001.pdf

Why self-host?

GDPR compliance – your data stays on your server
No monthly fees – pay only for your VPS (as low as €5/month)
Customizable – MIT license, fork it, brand it, extend it
API-first – integrate with your existing workflow (n8n, Zapier, custom apps)

Roadmap

[x] Core API (customers, invoices, PDF generation)
[x] Stripe webhook integration
[x] Docker deployment
[x] OpenAPI auto-documentation
[ ] Multi-currency support
[ ] Email delivery (SendGrid/Mailgun)
[ ] Recurring invoices
[ ] React admin dashboard

Try it now

git clone https://github.com/UniTy/invoice-api.git

⭐ Star the repo if you find it useful! Feedback and PRs welcome. 🙏

#invoicing #api #fastapi #python #stripe #opensource #docker

DEV Community: Maxence Londot