How is a German Steuer-ID validated?

Three rules apply. The first digit must not be zero. Within the first ten digits exactly one digit value repeats (appearing two or three times) while every other value appears at most once. The eleventh digit is an ISO 7064 MOD 11,10 check digit computed over the first ten. This tool implements all three exactly.

What is the Steuerliche Identifikationsnummer?

It is Germany's permanent 11-digit personal tax identification number (also called Steuer-ID or IdNr), issued once by the Bundeszentralamt für Steuern and used for life. It is different from the Steuernummer issued by your local tax office.

How does the MOD 11,10 check digit work?

ISO 7064 MOD 11,10 runs a product through the first ten digits — start with a remainder of 10, and for each digit compute ((remainder + digit) mod 10, or 10 if zero) × 2 mod 11. The check digit is 11 minus the final remainder (0 if that gives 10).

What is the digit-frequency rule?

Across the first ten digits, exactly one digit value may repeat — appearing two or three times — while every other value appears at most once. A number like 1234567890 fails because no digit repeats; the repeat is part of the official spec.

Is the Steuer-ID the same as a VAT ID?

No. The Steuer-ID is a personal tax number for individuals. The VAT ID (USt-IdNr) is for businesses doing EU trade and has the form DE followed by 9 digits.

Does a valid result mean the Steuer-ID is real?

No. A pass means the number is structurally and mathematically well-formed. It cannot confirm the ID is issued, active or linked to a specific person — only the Bundeszentralamt für Steuern holds that data.

Is my Steuer-ID sent anywhere?

No. Validation is entirely client-side — the number never leaves your browser and there are no network requests.

Germany Steuer-ID Validator (Steuerliche Identifikationsnummer)

This tool validates a German Steuer-ID (Steuerliche Identifikationsnummer / IdNr) — the permanent 11-digit personal tax number issued for life by the Bundeszentralamt für Steuern. It checks the structure and the official check digit offline, which is useful for catching typos in forms, payroll records, and onboarding data before submission.

How it works

A Steuer-ID passes only when all three official rules hold:

First digit not zero — the leading digit must be 1–9.
Digit-frequency rule — across the first ten digits, exactly one digit value repeats (appearing two or three times) while every other value appears at most once.
ISO 7064 MOD 11,10 check digit — the eleventh digit is computed over the first ten. The algorithm starts with a remainder of 10 and, for each digit, sets the remainder to ((remainder + digit) mod 10, or 10 if 0) × 2 mod 11; the check digit is 11 − final remainder (0 if that equals 10).

Each rule is shown individually so you can see exactly why a number passes or fails. The tool validates the documented format only — it does not query any tax-office database.

Example

Take any candidate Steuer-ID and the tool checks it in this order:

First digit — if it is 0, the number fails immediately (e.g. 02476291358 is rejected because it starts with zero).
Digit frequency — the first ten digits must contain exactly one repeated value; a number like 1234567890 fails because no digit repeats.
Check digit — the eleventh digit must equal the MOD 11,10 result over the first ten; changing any single digit normally breaks this.

A green “Valid” result means all three checks pass and the number is structurally well-formed.

Rule	What it verifies
First digit	Leading digit is 1–9, never 0
Digit frequency	Exactly one repeated value in the first 10 digits
Check digit	11th digit = ISO 7064 MOD 11,10 over digits 1–10

Privacy-first: the Steuer-ID is processed entirely in your browser — nothing is uploaded or sent anywhere.