Building Invoice Integrations for Germany? Meet the Kontelio API and Open-Source SDKs

Paulo Roberto Balmer — Mon, 19 Oct 2026 13:08:08 +0000

If you're building a SaaS platform, ERP, CRM, or business application for the German market, you've probably encountered a common challenge: German invoicing requirements can get complicated.

Between VAT regulations, structured electronic invoices, XRechnung, ZUGFeRD, and integration with existing business systems, implementing invoicing functionality requires more than generating a PDF.

That's why we created Kontelio, a multilingual accounting and invoicing platform for freelancers, self-employed professionals, and small businesses in Germany.

And to make integrations easier for developers, we've introduced the Kontelio API and open-source SDKs.

Why integrate invoicing instead of building everything yourself?

Imagine you're developing:

An ERP that needs to generate invoices automatically.
A CRM that creates invoices when deals are completed.
A SaaS platform that bills customers for subscriptions.
An e-commerce application that needs German-compliant invoicing workflows.
An internal business tool that synchronizes billing information.

Instead of developing and maintaining an entire invoicing subsystem, you can integrate with a dedicated invoicing platform.

Introducing the Kontelio SDKs

We've made integration resources available for developers working with JavaScript, TypeScript, Node.js, and Java.

JavaScript / TypeScript SDK

Available on npm:

@kontelio/sdk

Open-source GitHub repository

Explore the source code, documentation, and integration examples:

Kontelio SDK on GitHub

The goal is to simplify API integration and help developers connect their applications with Kontelio's invoicing capabilities.

Built for the German market

German invoicing introduces requirements that international billing platforms don't always address in the same way.

Kontelio is designed around the needs of businesses operating in Germany, including:

Invoice management
Electronic invoicing workflows
XRechnung and ZUGFeRD support
German VAT requirements
Accounting workflows for freelancers and small businesses
Multilingual interfaces

The platform also supports accounting-related functionality such as EÜR and German tax reporting workflows.

More than just an invoicing tool

Kontelio is designed to make accounting easier for people running businesses in Germany, including international entrepreneurs who prefer working in their native language.

By exposing integration capabilities, we want to help developers connect existing business applications to German invoicing and accounting workflows.

Getting started

If you're interested in exploring the integration:

Visit the Kontelio website.
Explore the SDK repository on GitHub.
Check the JavaScript/TypeScript package on npm.
Review the SDK documentation for authentication, available operations, and integration examples.

You can also explore Kontelio with a 30-day free trial.

Let's connect!

We're interested in hearing from developers building applications for the German market.

What has been your biggest challenge when implementing invoicing or accounting integrations in Germany?

Have you worked with XRechnung, ZUGFeRD, or German invoicing APIs?

Share your experience in the comments!

Resources

Website: https://www.kontelio.de/
GitHub: https://github.com/balmer-systeme/kontelio-sdk
npm: https://www.npmjs.com/package/@kontelio/sdk

Disclosure: I'm involved in developing Kontelio and its integration SDKs.

api #javascript #typescript #opensource

DEV Community: Paulo Roberto Balmer