e-Rechnung Inbox: an audit-ready invoice intake for Germany's e-invoicing mandate
An in-house product for a process that gets audited — official KoSIT validation, tamper-evident archiving, DATEV-ready export.
Challenge
From 2025 German businesses must be able to receive structured e-invoices. The difficulty is not the format but the reality around it: suppliers keep sending PDFs and scans for months, while standard tooling assumes compliant XML already arrives. At the same time invoice intake is a process that gets audited — whatever is built here has to survive a tax audit, not merely work. That combination of format variety, legal weight and burden of proof was the real brief.
Solution
We built invoice intake as a standalone, audit-ready process rather than a format converter. Each organisation gets its own inbound address; documents arrive by email, upload or watched folder. Validation runs in four stages — format, profile, business rules and cross-checks — against EN 16931 using the official KoSIT validator, the same tool German public administration relies on. Tax numbers and VAT IDs are checked against BZSt and VIES and cached. Every document is stored with a SHA-256 hash, timestamp and audit trail, and immutability is enforced by database triggers rather than by the application. A status track from "new" to "paid" keeps the approval path traceable, and export produces a complete tax-advisor package of originals, previews, manifest and booking suggestions.
Technologies
Results
Four-stage validation against EN 16931 using the official KoSIT validator
Tamper-evident archiving: SHA-256, timestamps, immutability enforced by database triggers
Tax number and VAT ID checked against BZSt and VIES
DATEV-ready tax-advisor package; operated in Frankfurt (eu-central-1)