automationsmanufaktur-labs/open-invoice-germany

OpenInvoice Germany is free, self-hosted invoicing software built for German legal and tax requirements. The motivation is practical: Germany introduced a rule requiring all B2B businesses to accept structured electronic invoices from 2025, with mandatory sending coming in 2027 and 2028. Many freelancers and small businesses pay monthly fees for compliant invoicing tools. This project provides the same compliance for free, with all data stored on your own machine. The software handles the specifics of German invoicing law. It generates XRechnung and ZUGFeRD format e-invoices, which are the structured electronic formats Germany requires. It enforces the mandatory fields under Section 14 of the German tax code (UStG) and blocks you from finalizing an invoice that is missing required information. It also implements GoBD requirements, the German rules for proper bookkeeping records: invoices become immutable once finalized, invoice numbers are gapless, and every change is recorded in an audit hash chain. It supports standard VAT rates, the small business exemption under Section 19, reverse charge, and intra-EU supply rules. Beyond invoicing, the software covers quotes, order confirmations, partial payments, credit notes, dunning letters with legally correct default interest calculations, and recurring invoice templates. Exports include PDF and the structured XRechnung XML. An optional feature lets you connect the application to Claude Code or Claude Desktop via MCP (a protocol that lets AI assistants call external tools). With this set up, you can describe an invoice in plain language and the AI handles the steps. The README includes a clear privacy note: customer names and amounts sent this way go to the AI provider's cloud, so for real business data you would need either a local AI model or a provider with a formal data processing agreement. Setup runs locally with SQLite and no server required, or with PostgreSQL via Docker. The project is licensed under AGPL-3.0, which requires anyone who offers it as a network service to publish their modified source code. The authors explicitly state this is not legal or tax advice, and that GoBD compliance also requires your own process documentation.