Which ID this page means
Germany’s personal tax ID is the Steueridentifikationsnummer (often called Steuer-ID). It is different from a local tax office file number used on some assessments.
How newcomers usually get it
After you register your residence (Anmeldung), the tax ID is generally sent by post. Make-it-in-Germany and BZSt describe the process. If the letter never arrives, BZSt explains how to request the number.
What this page does not do
It does not replace Anmeldung, and it does not assign you a tax class (Steuerklasse).