Eingang

An open-source inbox for supplier invoices, built for small German businesses as e-invoicing becomes mandatory. It tells an XRechnung from a ZUGFeRD hybrid from a plain PDF, validates real e-invoices against the official KoSIT rules, and explains each failed rule in plain language. Plain PDFs are read by an LLM, and every value it returns shows the line it came from and how sure it is.

The model only reads; code computes and checks. Sixteen business checks catch duplicates, a changed bank account, totals that do not add up, and a PDF that disagrees with its own XML. Nobody approves an invoice they reviewed themselves, and approved invoices leave as a CSV and a ZIP of originals for the tax advisor. Each document runs as its own durable Temporal workflow, so a slow model call or a worker restart picks up where it stopped.

Every number is measured, including the weak ones. Validation matches the official KoSIT validator on all 176 test files, same verdict and same failed rules. AI extraction gets all four critical fields right on 65.4% of invoices against 21.2% for a regex baseline, on a corpus of only 33 distinct invoices, and the write-up says so. It costs $0.000321 per invoice.