Germany Steuer-ID Checksum Validator (ISO 7064)

How to Use the Germany Steuer-ID Checksum Validator

1. Type or paste an 11-digit Steuer-ID into the box above — spaces are fine, the tool strips them automatically.
2. Click Check. The tool verifies the number is 11 digits, doesn't start with 0, and recomputes the ISO 7064 MOD 11,10 check digit.
3. Read the decode table showing the identification digits and the check digit separately.
4. Nothing you type is uploaded anywhere — the whole calculation runs as plain JavaScript in your browser tab.

What the Steuer-ID Is

The Steueridentifikationsnummer (Steuer-ID, or IdNr) is an 11-digit personal tax identification number introduced in Germany in 2008 under §139b of the Abgabenordnung (Fiscal Code). Every resident is assigned one for life — it doesn't change when you move, marry, or change your name, and it stays valid for 20 years after death, used exclusively for income tax purposes across every Finanzamt (tax office) in the country.

Unlike France's NIR or Italy's Codice Fiscale, the Steuer-ID deliberately encodes no personal information whatsoever — no birth date, no region, no gender. It's a random 11-digit number subject to two structural rules: it never starts with 0, and among the first 10 digits, exactly one digit must repeat two or three times (a rule designed to make the ID space large enough while keeping numbers memorable). This tool checks the check digit; it does not additionally verify that digit-repetition rule.

The Checksum: ISO 7064 MOD 11,10

The 11th digit is a check digit computed using the ISO 7064 MOD 11,10 algorithm — an international standard for check-digit systems, also used for other identifiers around the world. The calculation processes the first 10 digits one at a time, maintaining a running "check" value that starts at 5, doubles and reduces modulo 11 at each step, and folds in the next digit modulo 10. The final check digit is derived from that running value with a similar reduction. It's not something you'd want to compute by hand, but it reliably catches single-digit errors and most transpositions — exactly the errors people make copying an 11-digit number from a letter or ID card.

Worked Example

What This Tool Does NOT Do

This checks the 11-digit format and the ISO 7064 MOD 11,10 check digit only. It does not verify the official "exactly one repeated digit among the first 10" structural rule, and it does not query the Bundeszentralamt für Steuern (BZSt) database — it cannot confirm a Steuer-ID is actually issued or belongs to a real person. Because the number carries no embedded personal data, there's nothing further to decode beyond the digits themselves and the check digit.

Common Mistakes

• Confusing the Steuer-ID with the Steuernummer (a different, tax-office-specific number that changes when you move) or the USt-IdNr (VAT number)
• Assuming the digits encode a birth date or region — they deliberately don't
• Dropping a leading digit when copying from a form, which shifts every position and breaks the checksum
• Treating a checksum pass as proof the ID is currently active — this tool has no way to know that

Frequently Asked Questions

Is my Steuer-ID uploaded anywhere? No — everything runs locally in your browser tab.

Is the Steuer-ID the same as the Steuernummer? No — the Steuer-ID is a lifetime personal number; the Steuernummer is tied to a specific tax office and can change.

Does a valid checksum mean the ID is real? No — it means the number is internally consistent, not that it's actually issued.

Is this tool free? Yes, completely free, with no login and no usage limit.