Austrian Firmenbuchnummer
Generator
Generate properly formatted Austrian Firmenbuchnummer (FN) company registration numbers that pass the official BMJ check-letter algorithm — for software testing, entirely in your browser.
About Austrian Firmenbuchnummer
The Firmenbuchnummer is the official registration code for Austrian commercial companies (GmbH, AG), administered by the Federal Ministry of Justice (BMJ).
Formatted as 'FN XXXXXX y' — up to six digits plus a lowercase check letter.
Anatomy of Austrian Firmenbuchnummer
| Position | Field | Length | Meaning & Rule | Example |
|---|---|---|---|---|
| 1 to 3 | Optional Prefix | 3 characters | Prefix 'FN' indicating commercial register | FN |
| 4 to 9 | Sequential Number | 1 to 6 digits | Sequential registration number in commercial court | 575737 |
| 10 | Check Letter | 1 letter | Lowercase check letter from the BMJ lookup table | y |
Official Modulo 17 Algorithm
| Step | Description |
|---|---|
| 1. Weight each digit | Multiply the six digits (left-padded with zeros if fewer than six) by the fixed weights 6, 4, 14, 15, 10, 1, in that order. |
| 2. Sum the weighted products | Add all six weighted products together. |
| 3. Reduce modulo 17 | Calculate the remainder of the sum divided by 17 (Sum % 17). |
| 4. Look up the check letter | Use the remainder (0 to 16) as an index into the 17-letter table a, b, d, f, g, h, i, k, m, p, s, t, v, w, x, y, z to get the check letter. |
Frequently Asked Questions
What is the difference between FN and UID?
FN (Firmenbuchnummer) is the company's registration number in Austria's commercial register (Firmenbuch), administered by the Federal Ministry of Justice. UID (Umsatzsteuer-Identifikationsnummer) is the separate Austrian VAT number, administered by the tax authority, used for EU cross-border VAT purposes. A company has both, independently of each other.
Is the "FN" prefix mandatory?
The underlying number and check letter are what matter for validation — "FN" is a conventional display label commonly shown on official documents and the business register, but systems and forms may store or accept just the digits and check letter without it.
Are the generated numbers official or real?
No. These are synthetic numbers generated purely to satisfy the Firmenbuchnummer check-letter formula for software testing. They are not issued by the BMJ, not linked to any real company, and must never be used on real filings, contracts, or official documents.