Your Identity in the German Tax System
Upon moving to Germany and completing your 'Anmeldung' (registration), you will automatically receive a 'Steuerliche Identifikationsnummer' (Steuer-ID) by mail. This is a permanent, lifelong 11-digit number used for employment and banking. However, if you are self-employed or have complex tax affairs, the Finanzamt will also issue a 'Steuernummer' (tax number), which is local to your specific tax office. For US expats, the Steuer-ID is what your German bank will ask for to comply with FATCA. Without it, they may withhold higher taxes or even close your account. Visit the Federal Central Tax Office (BZSt) if you lose your ID.
FATCA Reporting
German banks use your Steuer-ID to report your account information back to the IRS under the Intergovernmental Agreement (IGA).
Managing Tax IDs Across Borders
In 2026, the 'Steuer-ID' is also used for the German 'Kirchensteuer' (Church Tax) and 'Solidaritätszuschlag' (Solidarity Surcharge) calculations. The relationship is: $$Tax_{Total} = Income\\ Tax + (Income\\ Tax \\times Rate_{Soli}) + Church\\ Tax$$. LSI keywords include 'Finanzamt,' 'ELSTER,' 'Tax Class (Steuerklasse),' 'Freiberufler,' and 'FATCA IGA.' When filing your US return, you don't typically need to provide your German Steuer-ID to the IRS, but you *must* provide your US SSN to your German bank. Refer to the US Treasury FATCA Resource Center for more on international data sharing. If you are a freelancer, your Steuernummer will change if you move cities, whereas your Steuer-ID remains the same. Understanding this distinction is key to navigating the ELSTER online portal for your German filings.