Field help:
(2023)
Your tax number (Steuernummer)
Tax reference number for <%0100801%>
You can find your current tax number (Steuernummer) in your tax office documents, for example, in your last tax assessment notice (Steuerbescheid).

The tax number (Steuernummer) should not be confused with the tax identification number (Steuer-Identifikationsnummer), which is valid for life.