🪪German Tax ID Validator (Steuer-ID)

Steuer-ID Validator — check a German tax identification number online

The Steuer-Identifikationsnummer (Steuer-IdNr) is an 11-digit tax identification number assigned by the Bundeszentralamt fuer Steuern (BZSt) to every individual registered in Germany. Unlike the Umsatzsteuer-Identifikationsnummer (USt-IdNr / VAT-ID), which businesses use for intra-EU VAT transactions, the Steuer-IdNr applies exclusively to individuals and is used for income tax (Einkommensteuer) purposes.

Our free validator checks three conditions: the correct number of digits (exactly 11), the digit uniqueness rule required by BZSt, and the check digit calculated using the ISO 7064 MOD 11,10 algorithm. The result appears instantly as you type.

Check digit algorithm

The last (11th) digit of the Steuer-IdNr is a check digit calculated using the ISO 7064 MOD 11,10 algorithm. The algorithm processes the first 10 digits in sequence: starting with product = 10, for each digit it calculates sum = (digit + product) mod 10 (if 0, use 10), then product = (sum * 2) mod 11. The final check digit = (11 - product) mod 10. The number is valid when the 11th digit equals this value.

Privacy — fully local processing

Validation takes place entirely in your browser. No digit of the entered number is sent to any server. You can validate numbers even offline.

Frequently asked questions

What is the Steuer-Identifikationsnummer (Steuer-IdNr)?

The Steuer-Identifikationsnummer (Steuer-IdNr or IdNr) is an 11-digit tax identification number assigned to every individual residing in Germany by the Bundeszentralamt fuer Steuern (BZSt). It is permanent, unchanging, and remains valid even after a change of address, marital status, or surname.

How does the Steuer-IdNr differ from the USt-IdNr (VAT ID)?

These are two completely different numbers. The Steuer-IdNr identifies individuals for general taxation purposes (income tax). The USt-IdNr is a VAT identification number for businesses operating in the EU and is used for intra-EU commercial transactions. The USt-IdNr starts with the letters DE and has 9 digits.

How does the Steuer-IdNr checksum algorithm work?

The check digit (11th digit) is calculated using the ISO 7064 MOD 11,10 algorithm: starting with product = 10, for each of the first 10 digits compute sum = (digit + product) mod 10 (if 0, use 10), then product = (sum * 2) mod 11. Finally pruefziffer = (11 - product) mod 10.

What is the digit uniqueness rule in the Steuer-IdNr?

The Bundeszentralamt fuer Steuern requires that among the first 10 digits, exactly one digit repeats 2 or 3 times, while all other digits appear at most once. If a digit appears 3 times, those three occurrences must not be directly adjacent. The first digit must not be zero.

Is my data sent to a server?

No. All validation is performed locally in your browser. Not a single digit of the entered number reaches any server. You can use the validator even without an internet connection.