What the Steuer-ID looks like
The tax identification number consists of ten digits and a check digit as the eleventh digit (§ 1 StIdV). It contains no letters.
It is not formed from other data about the person, such as name or date of birth (§ 139a Abs. 1 Satz 2 AO). Nothing about the person can be read from the number.
Does this number have the form of a Steuer-ID?
Nothing entered yet.
Only the form is checked: 11 digits, no letters (§ 1 StIdV). Spaces are ignored.
The result does not say whether the number has been issued or belongs to a particular person.
The check digit is not recalculated, because the method for it has not been officially published.
Your entry does not leave your browser.
It stays for life
Each person receives only one number, and each number is issued only once (§ 139b AO).
According to the Federal Central Tax Office (Bundeszentralamt für Steuern), it is permanently valid. It does not change with a move, a change of name or a change of marital status.
Do not confuse
Anyone who is economically active also receives a business identification number (Wirtschafts-Identifikationsnummer) (§ 139a Abs. 1 Satz 3 AO). That is a different number.
Where to find it
According to the Federal Central Tax Office, the number is usually shown in the income tax assessment or on the annual wage tax statement.