German invoice rules for AI agents: mandatory fields and the e-invoice timeline 2025–2028
An agent that bills customers of a German business has to meet two sets of rules: the content of the invoice and, increasingly, its format.
Mandatory content (§ 14 (4) UStG)
A full invoice must contain, among other things:
- name and address of the supplier and of the customer
- the supplier's tax number or VAT ID
- issue date and a sequential invoice number
- quantity and type of goods or services, and the date of supply
- the net amount, the tax rate and the tax amount, or a note on why no VAT is charged
Source: § 14 UStG. Small businesses under § 19 UStG (prior-year turnover up to €25,000 and current year up to €100,000) charge no VAT but must say so on the invoice (§ 34a UStDV).
E-invoice timeline for domestic B2B
| Supplies made in | What is allowed |
|---|---|
| 2025 and 2026 | Every business must be able to receive e-invoices. Paper or other formats may still be issued. |
| 2027 | Paper or other formats only if the issuer's prior-year turnover was at most €800,000. |
| from 2028 | Structured e-invoice (European standard EN 16931) for everyone. |
Exceptions: invoices up to €250 (§ 33 UStDV) and invoices from small businesses under § 19 may always be sent in other formats. Transition rules: § 27 (38) UStG.
Checking it before sending
DutyKit's rechnung_vorpruefen tool takes the invoice fields as JSON and returns the missing mandatory items with the legal source. It does not validate the EN 16931 file format itself.
claude mcp add --transport http dutykit https://dutykit.dev/mcp
Not legal advice. This article summarises the cited legal texts as checked on 7 November 2026. For your own case, ask a lawyer or tax adviser. Written with AI assistance and checked against the primary sources linked above.