---
title: "Guides"
description: "Step-by-step guides for integrating the Billabex public API."
canonical: https://developer.billabex.com/en/guides/
lang: en
alternate: https://developer.billabex.com/fr/guides/
last-updated: 2026-09-12
---

# Guides

> Step-by-step guides for integrating the Billabex public API.

Source: https://developer.billabex.com/en/guides/
Language: English (en)
French version: https://developer.billabex.com/fr/guides/

- [Getting Started](https://developer.billabex.com/en/guides/getting-started/): Quick introduction to the Billabex API. Learn how to authenticate and make your first API call.
- [Billabex OAuth Authentication](https://developer.billabex.com/en/guides/oauth/): OAuth 2.1 Authorization Code flow with PKCE and optional OpenID Connect for Billabex.
- [OAuth Scopes](https://developer.billabex.com/en/guides/scopes/): Understand available OAuth scopes, how access is enforced, and how to request the right permissions for your integration.
- [JSON Errors](https://developer.billabex.com/en/guides/errors/): Parse Billabex API errors by code, use the resolution hint, and retry only when the response allows it.
- [Idempotency](https://developer.billabex.com/en/guides/idempotency/): Make a retried write safe: send an Idempotency-Key and a second attempt replays the first answer instead of creating a second record.
- [Billabex MCP Server](https://developer.billabex.com/en/guides/mcp/): Connect AI tools to Billabex using the Model Context Protocol (MCP) with OAuth 2.1.
- [Notification Preferences](https://developer.billabex.com/en/guides/notification-preferences/): Read and update the authenticated user notification preferences.
- [Rate Limiting](https://developer.billabex.com/en/guides/rate-limiting/): Understand the OAuth token rate-limiting model, why it is designed this way, and what your integration should implement.
- [Audit Journal](https://developer.billabex.com/en/guides/audit-journal/): Read who did what in an organization: one entry per successful command, filterable by account, actor and free text.
- [Pagination & Filtering](https://developer.billabex.com/en/guides/pagination/): Understand Billabex cursor pagination and the filters parameter, and what your integration should implement.
- [Account Sources](https://developer.billabex.com/en/guides/sources/): Learn how to link and unlink external data sources to accounts via the API.
- [Original invoice of a credit note](https://developer.billabex.com/en/guides/credit-note-original-invoice/): Link a credit note to the invoice it came from, without creating an allocation or moving any balance.
- [Upsert Operations](https://developer.billabex.com/en/guides/upsert/): Create or update resources in a single idempotent request using upsert endpoints.
- [Contacts](https://developer.billabex.com/en/guides/contacts/): Manage customer contacts associated with accounts.
- [File Uploads](https://developer.billabex.com/en/guides/file-uploads/): Upload invoice, credit note and email attachment files using binary or base64 encoding.
- [Account Tasks & Interactions](https://developer.billabex.com/en/guides/account-tasks/): Respond to Billabex agent account tasks: search, list, get, cancel, set aside, and add user interactions.
- [Send an SMS or a letter](https://developer.billabex.com/en/guides/outgoing-messages/): Preview, price, and send a paid follow-up without creating a duplicate.
- [Read the aging balance](https://developer.billabex.com/en/guides/aging-balance/): Analyse net outstanding amounts by age bucket, currency, and customer account.

---

Billabex developer portal. OpenAPI specification: https://developer.billabex.com/openapi.json.
Agent instructions: https://developer.billabex.com/llms.txt. Complete documentation: https://developer.billabex.com/llms-full.txt.