USt-IdNr.
The German VAT identification number used for intra-EU B2B transactions, distinct from the domestic Steuernummer.
What it is
The Umsatzsteuer-Identifikationsnummer (USt-IdNr.) is Germany's EU-facing VAT number. It takes the form DE followed by exactly 9 digits (e.g. DE123456789), giving an 11-character string. The final digit is a MOD-11 check digit, which means a typo in any digit position can be caught before the number is submitted to a registry.
Where you meet it
The USt-IdNr. appears on cross-border B2B invoices between EU member states and in the requester_vat_number field when calling /v1/confirm for a §18e BZSt qualified confirmation. It is also the number queried through VIES to confirm that a German counterparty is currently VAT-registered in Germany.
How it differs from the Steuernummer
The Steuernummer is issued by the regional Finanzamt for domestic income tax purposes. It is 10-13 digits depending on the Bundesland format and encodes the regional tax office. The Steuernummer is not valid for EU cross-border VAT purposes and will not resolve in VIES.
German businesses therefore hold two separate numbers: the Steuernummer for domestic filings with their Finanzamt, and the USt-IdNr. for EU-facing transactions. Customers frequently supply the wrong number when asked for their VAT number for an invoice, which is the most common cause of invalid_format errors in vatverify for DE-prefixed inputs.
How to obtain one
A German business applies for the USt-IdNr. through the Finanzamt that issued their Steuernummer. The Finanzamt forwards the application to BZSt, which issues the EU-facing number. The process can take several weeks.