The tax ID (Steueridentifikationsnummer, Steuerliche Identifikationsnummer, Persönliche Identificationsnummer, Identifikationsnummer, Steuer-IdNr., IdNr or SteuerID) is a unique identification number all German residents receive. This is the number the tax office (Finanzamt) uses to identify you. It has the format "12 345 678 901". You receive that number after registering your address in Germany.

The tax ID is also called a Steuerliche Identifikationsnummer, Persönliche Identificationsnummer, Identifikationsnummer, Steuer-IdNr., IdNr or SteuerID. The tax ID is not the same as the tax number (Steuernummer).

When you start working in Germany, you must give your tax ID to your employer. Your employer needs your tax ID to calculate your income tax.

For more details, see this guide.