German Steuer-ID Validator
ValidatorValidate German Steuer-ID numbers. Recomputes the official MOD 11,10 check digit and verifies the §139b AO digit-repetition rule. Runs entirely in your browser.
About this tool
About German Steuer-ID Validator
This validator checks whether an 11-digit German Steuer-ID is structurally valid: it recomputes the official MOD 11,10 check digit and verifies the §139b AO digit-repetition rule (exactly one digit repeated twice or three times among the first 10 digits).
The validator strips whitespace, checks the 11-digit format and that the first digit isn't zero, recalculates the check digit using the official algorithm, and separately verifies the digit-repetition pattern — reporting exactly which check failed if the number is invalid.
Use this to verify a Steuer-ID collected from a form before submitting it to a German tax or payroll system, to debug why a number is being rejected, or to confirm generated test data is structurally correct.
Instant, fully client-side validation with no data ever leaving your browser. Note this checks structural validity only — it does not confirm the number is actually assigned to a real person by the Bundeszentralamt für Steuern.
Key Features
- Recomputes the official MOD 11,10 check digit
- Verifies the §139b AO digit-repetition rule
- Clear pass/fail reporting for each individual check
- Handles both the pre-2016 and 2016+ repetition patterns
- 100% browser-based, no data ever transmitted
FAQ
German Steuer-ID Validator — Frequently Asked Questions
What does this validator actually check?
It checks that the input is exactly 11 digits with a non-zero first digit, recomputes the 11th digit using the official ISO/IEC 7064 MOD 11,10 algorithm, and separately verifies that the first 10 digits follow the §139b AO digit-repetition rule. Both checks must pass for the number to be marked valid.
Does this check the Bundeszentralamt für Steuern database?
No. This tool performs structural and check-digit validation entirely in your browser. To confirm a Steuer-ID is actually assigned to a real person, you would need an official verification channel — there is no public lookup service.
My number fails the digit-repetition check — is my Steuer-ID wrong?
Not necessarily a typo in the check digit itself, but it does mean the first 10 digits don't follow the official pattern (exactly one digit repeated twice with one digit missing, or repeated three times — not consecutively — with two digits missing). Double-check you copied all 10 base digits correctly.
What's the difference between Steuer-ID and Steuernummer?
The Steuer-ID is a permanent 11-digit personal number assigned for life. The Steuernummer (tax number) is assigned per tax office and business/individual, changes if you move to a different Finanzamt jurisdiction, and has a different, region-specific format. This validator checks Steuer-ID only.
Tips
- The Steuer-ID has no letters — if your number contains letters, you may have a Steuernummer instead
- A check-digit mismatch usually means a single mistyped digit
- Cross-check against the physical letter (Mitteilung über die Erteilung der Steuer-Identifikationsnummer) you received from the Bundeszentralamt für Steuern
- Use the Steuer-ID Generator to see a correctly formed example
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