Developer Portal

Build powerful integrations with Billabex

Automate invoice dunning with an AI-powered platform. Integrate seamlessly with our REST API, OAuth 2.1 authentication with PKCE, and comprehensive documentation.

Get started API reference
REST API OAuth 2.1 OpenAPI

Production-ready endpoints with cursor-based pagination, token-based rate limiting, and OAuth 2.1 security. 

https://next.billabex.com/api/public/v1

What is Billabex?

Billabex is an AI-powered invoice dunning automation platform that helps businesses recover outstanding payments faster. Our intelligent agent handles customer follow-ups in multiple languages, with tact and diplomacy.

Intelligent responses — AI understands customer replies and adapts communication
Multilingual support — Communicate with customers in their preferred language
API-first platform — Integrate with your billing tools and workflows

Developer experience

Production-ready features

OAuth 2.1 with PKCE — Secure authorization code flow
Cursor-based pagination — Efficient handling of large datasets
Rate limiting — Token-based limits with clear headers
Comprehensive scopes — Granular permission control
OpenAPI documentation — Interactive API explorer
File uploads — Multipart form-data for invoices and credit notes

Quick start

  1. Create an OAuth client in Developer Portal > OAuth Clients
  2. Implement the authorization code flow with PKCE
  3. Exchange authorization code for access and refresh tokens
  4. Fetch your organizationId from GET /organizations
  5. Call the public API with your access token
  6. Handle pagination and rate limits
Start building

Explore the API

Guides

Step-by-step tutorials for authentication, pagination, rate limiting, and more.

API reference

Complete endpoint documentation with request/response schemas and live examples.

OAuth authentication

Secure your integration with OAuth 2.1 authorization code flow, PKCE, and optional OIDC.

OAuth scopes

Understand available permissions for invoices, accounts, communications, and organizations.

Ready to start building?

Follow our getting started guide to make your first API call in minutes. Learn how to authenticate, handle pagination, and manage resources programmatically.

Read getting started Explore API reference