This German Steuer-ID validator checks a Steuerliche
Identifikationsnummer against both of its structural rules: the digit-repetition pattern
and the official ISO 7064 checksum used by the Bundeszentralamt für Steuern. Nothing you
type leaves your browser.
How to use it
Enter the 11-digit Steuer-ID and click "Check Steuer-ID". The tool first confirms the
first digit isn't zero and that exactly one digit value repeats among the first ten digits,
then verifies the 11th digit against the computed checksum.
How the checksum works
The algorithm (ISO 7064 MOD 11,10) processes the first ten digits one at a time, carrying a
running "product" value that starts at 10: each digit is added to the product modulo 10
(treating a zero result as 10), then doubled and reduced modulo 11 to become the next
product. The final check digit is derived from 11 − product, wrapping 10 to 0.
This construction is sensitive to single-digit errors and adjacent-digit transpositions —
exactly the typos it exists to catch.
Why the digit-repetition rule exists
Unlike a pure checksum, the repetition rule is a structural property baked into how Steuer-
IDs are generated, on top of the checksum. A number can accidentally satisfy the checksum
formula while violating the repetition rule, so a real Steuer-ID must pass both checks, not
just one.
Frequently asked questions
What is a Steuer-ID?
The Steuerliche Identifikationsnummer (Steuer-ID, or "Steueridentifikationsnummer") is an 11-digit number every person registered in Germany is assigned for life, used across tax offices, employers, and health insurers. It's different from the Steuernummer (tax number), which changes if you move or change tax office.
What is the digit-repetition rule?
Among the first 10 digits, exactly one digit value must repeat — either twice, or three times with the three occurrences not all directly adjacent — and every other digit value must appear at most once. This is a deliberate structural constraint, not just a checksum, published by the Bundeszentralamt für Steuern (BZSt).
How is the 11th digit calculated?
It uses the ISO 7064 MOD 11,10 checksum algorithm: a running "product" value starts at 10, and for each of the first 10 digits it's updated based on that digit, ending in a formula that derives the check digit from the final product. The same algorithm is used for the German VAT number's check digit.
Can this tool confirm my Steuer-ID belongs to me?
No. The BZSt does not offer a public API to verify that a Steuer-ID is actually assigned and active. This tool only checks structural validity — the digit rule and checksum — which catches typos and mistyped numbers, not whether the number was genuinely issued.
Is my Steuer-ID sent anywhere when I use this tool?
No. Validation happens entirely in your browser via JavaScript. Nothing is transmitted, logged, or stored — worth caring about, since a Steuer-ID is a permanent personal identifier.