Difference between Steuernummer and VAT ID numbers (USt-IdNr)
The Steuernummer is the tax number issued by the tax office where the business is registered. It is used in VAT returns and for all correspondence, audits, and day-a-day issues with the tax authorities. The VAT ID number, often referred as USt-IdNr, is the VIES number, used for all intra-Community transactions.
A foreign business must first apply for a steuernummer at the corresponding tax office (in Germany, depending on your country of establishment, you are allocated a specific tax office). Once the steuernummer is received, an additional application must be made to the Federal Tax office to obtain the VAT Id number (USt-IdNr).