The format is a commodity. The last mile is not.
From 2027 German companies above 800,000 euros of prior-year revenue must issue structured e-invoices, from 2028 regardless of revenue, small businesses under the VAT exemption excepted. Standard software covers the format; what decides effort and risk is whether the system that actually creates the invoice today (industry software, ERP, spreadsheets) can produce EN 16931 output, and whether edge cases like public-sector clients or self-billing apply. Five questions per client sort that in about ten minutes.
Five questions, one traffic light per client.
Deadline (2027 or 2028), the system that creates the invoice, its EN 16931 capability at the installed version, edge cases (public sector, self-billing, complex allocation), and monthly volume. Green means configuration and a test; yellow means clarify updates with the vendor; red means a real integration is needed, a per-invoice converter is permanent manual work.
Built for the client conversation.
Tax advisors can run the triage across their client base to prioritise who needs to act in 2026. The client receives a confidentiality commitment (German sec. 203 StGB) and a data-processing agreement once the planned process is settled and the wording has been checked; the client contracts directly, the advisor stays in charge of the process. For engagements from October 2026 on, we accept files and access containing personal data only once the data processing agreement is signed. The full questionnaire below is in German, as are the legal specifics.