E-invoices that pass — XRechnung
via REST API.
XRechnung and ZUGFeRD from a single API, Peppol BIS 3.0 as a format. KoSIT-validated, GoBD-compliant, hosted in Germany. Start free, no credit card.
Where migrations actually fail
Not on the format. Producing the XML file is the smallest part of the work — the effort sits in the data your system has to supply for it.
- The routing ID (Leitweg-ID) of your public-sector customers is nowhere in the customer record.
- Credit notes need a reference to the original invoice that your system never stored.
- Tax categories work in the standard case but not for reverse charge or intra-community supply.
The recipient accepts the invoice technically but rejects it on substance — and nobody notices until the payment fails to arrive.
This data work happens once. After that the process runs. That is exactly the part we take on.
The readiness check
Free, no registration, and useful even if we never work together.
- Step 1
You send us a sample invoice
A real invoice from your system — as PDF, XML, or both. Plus a note on which system produced it and who it goes to.
- Step 2
We check it against the official rules
Validation against the KoSIT schemas and Schematron business rules — the same procedure public authorities and large recipients use on incoming invoices.
- Step 3
You receive a written finding
Within one working day: what passes, what is missing, which fields are unmaintained in your system — and an honest estimate of the effort.
The finding is yours. You can act on it yourself or hand it to another provider.
Have my invoice checkedTwo ways to e-invoicing
You build it in yourself, or we connect your system. Both start free.
E-invoicing via REST API
Create and validate XRechnung and ZUGFeRD from inside your own product. API key in 60 seconds, free tier without a credit card.
- KoSIT-validated — the same procedure the recipient runs
- Peppol BIS 3.0 as a format; dispatch over the Peppol network from Q3 2026
- Docs, playground and validator without registration
We connect it
Your ERP, your shop or your inventory system — including legacy and in-house builds. Fixed-price analysis first, then a proposal with a fixed timeline.
- Shopware, JTL, WooCommerce, Shopify, Sage, Xentral
- Analysis phase €950 — credited in full when you commission the work
- Connection then €6,000–15,000 at a fixed price, depending on scope
Your system doesn't speak to the API — we connect it.
We connect existing ERP, shop and inventory systems to the e-invoicing API — including legacy and in-house builds. Fixed price after a scoping call.
App development for iOS and Android
Alongside the e-invoicing API we build mobile apps for businesses: React Native and Flutter for both platforms from one codebase, Swift when it has to be native. From concept through store submission to running it after launch — an MVP is typically in the store within 8–12 weeks.
Two engineers, one product
xhub.io is a product of BeeBack UG in Frankfurt am Main, founded by two software engineers with more than 40 years of combined experience from projects for Deutsche Bahn, Mercedes-Benz and SMA Solar Technology.
Enterprise experience
Both founders come from projects for Deutsche Bahn, Mercedes-Benz and SMA Solar Technology. That experience is what the API is built on.
Dedicated account management
Direct access to your development team. No call centers, no ticket queues, no automated responses - just real people who know your business.
GDPR & security
Invoice data is processed in German data centres. A data processing agreement under Art. 28 GDPR is in place.
Agile & transparent delivery
Rapid iterations with bi-weekly releases, real-time project visibility, and continuous stakeholder communication throughout development.
How a connection runs
Five phases, fixed durations, fixed price. Scope is agreed up front so the price holds.
Analysis
Existing system, data model, recipients and your concrete legal obligation. The result states what actually has to be done.
3–5 daysMapping
Your master data is mapped onto EN 16931: mandatory fields, routing IDs, tax logic and the special cases every grown system has.
5–10 daysConnection
Technical integration into your system, including error handling and retry logic — so a rejected invoice surfaces instead of disappearing.
5–10 daysTest operation
Validation with real documents and, where possible, a dry run with an actual recipient. It goes live only once that holds.
3–5 daysGo-live
Cutover during running operations, handover to your team and documentation of what was mapped where.
2–3 daysOur Commitment to You
We reply to every inquiry within one business day — personally, from the developer who built the API. After the scoping call you get a fixed-price proposal.
What customers ask us most
No. The API sits next to your existing system, not in its place. You keep Shopware, JTL, WooCommerce, Shopify, Sage or your own grown in-house build — we take the invoice data, map it onto EN 16931 and return XRechnung or ZUGFeRD. Nothing about your process changes except the format that comes out at the end.
Let's start building together
Ready to transform your digital vision into reality? Let's discuss your project.
hello@xhub.io
Headquarters
Frankfurt am Main, Germany
Business Hours
Monday-Friday, 9:00-18:00 CET
Enterprise-grade quality
Fortune 500 standards with boutique agency agility
Dedicated partnership
Direct team access and custom-tailored solutions
Enterprise experience
From projects for Deutsche Bahn, Mercedes-Benz and SMA Solar