ZUGFeRD and Factur-X e-invoicing service: the E-Rechnung Pro case
How an online service for the EU market was built: creating, converting and validating e-invoices under EN 16931.
E-Rechnung Pro is RandomStar’s own service for businesses in Germany, France and other EU countries. It creates e-invoices in the ZUGFeRD and Factur-X formats, turns ordinary PDFs into such invoices and validates incoming ones.
The task
E-invoicing is gradually becoming mandatory across the EU: a PDF that carries the same data inside as XML under the EN 16931 standard. Large companies have accounting systems for that; a small business needs a simple tool in the browser, with nothing to install.
What was built
- Invoice creation. A form in the customer area that produces a PDF with embedded XML.
- PDF conversion. The service reads an ordinary PDF invoice, recognises the seller, buyer, line items and totals and builds a hybrid file from them.
- Validation. A check against EN 16931 with a list of errors.
- Customer area and subscription. Documents, profile, plans paid by card; up to 10 documents a month are free.
- A site in four languages. English, German, French and Ukrainian; a knowledge base and news on e-invoicing.
How it works
- Validation in a fraction of a second. The validator is a Java program that used to take about 8 seconds to start each time. It now runs permanently and stays warm: the check itself takes 0.1–0.4 seconds instead of 7.5, and the user sees the result within a second or two. A watchdog monitors it and restarts it on failure.
- The converter is measured on samples. There is a base of real invoices with different layouts; after every change the whole base is run again so that new code does not break what already worked. The converter passes 91 of 93 samples.
- Customer documents are private. A file is served only to its owner after a login check, never by a direct link.
- Automatic deployment. Changes reach the site right after checks, with no manual file copying.
The result
The service runs at zugferd.randomstar.org: more than 500 pages in Google search, and the first visitors arrive on their own — from search.
What you can order
A web service with a customer area, subscription and card payments; document work — PDF generation, parsing invoices and waybills, checks against a standard; connecting third-party programs to a site; a multilingual site built for search in other countries.
Got a task? Let’s talk
Send a request — the reply comes within a business day with a suggestion on how to do it.