E‑Rechnungen schreiben und empfangen mit BillingEngine

# BillingEngine > BillingEngine is online invoicing software for freelancers and small businesses in Germany. Every invoice is created as an e-invoice (ZUGFeRD and XRechnung, EN 16931), incoming e-invoices arrive in a dedicated inbox. It includes DATEV export, accountant access, a REST API and an MCP server. A permanently free plan is available. The interface is available in German and English. ## Product - [Features](https://www.billingengine.com/en/features): creating e-invoices, receiving e-invoices, quotes, revenue analysis - [Pricing](https://www.billingengine.com/en/pricing): plans and what each includes - [Help](https://www.billingengine.com/en/help): questions and answers ## Free tools (no sign-up, no file is stored) - [Tools overview](https://www.billingengine.com/en/tools): e-invoice generator, validator, viewer, Leitweg-ID (routing ID) checker, VAT calculator, default interest calculator ## For developers and AI assistants - [REST API](https://www.billingengine.com/en/api): documentation of the API - [OpenAPI description](https://www.billingengine.com/openapi.json): machine-readable description of the REST API - [MCP server](https://www.billingengine.com/en/mcp): connect AI assistants such as Claude or Cursor to your invoices ## Knowledge - [Glossary](https://www.billingengine.com/en/glossary): e-invoice, XRechnung, ZUGFeRD, EN 16931, GoBD, DATEV and more - [Templates](https://www.billingengine.com/en/templates): invoice and business document templates ## German version - [Deutsche Startseite](https://www.billingengine.com/de)

{ "openapi": "3.1.0", "info": { "title": "BillingEngine API", "version": "1.0.0", "summary": "REST API for customers, invoices and payments of BillingEngine.", "description": "BillingEngine is online invoicing software for freelancers and small businesses in Germany. Every invoice is an e-invoice (ZUGFeRD and XRechnung, EN 16931).\n\nThe API is available in the paid plans. Authenticate with the API key from your settings as a bearer token. All requests and responses use JSON;