Austrian Firmenbuchnummer (FN) Validator
Commercial company registration number in Austria (Firmenbuch / BMJ).
About Austrian Firmenbuchnummer
The official registration code for Austrian commercial companies (GmbH, AG).
Administered by the Federal Ministry of Justice (BMJ).
Anatomy of Austrian Firmenbuchnummer
Formatted as 'FN XXXXXX y' (1 to 6 digits plus a check letter):
| Position | Field | Length | Meaning | 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 | 123456 |
| 10 | Check Letter | 1 letter | Lowercase check letter from BMJ lookup table | k |
Official Modulo 29 Algorithm
Standard calculation by the Federal Ministry of Justice (BMJ):
Sum = Σ(d[i] * w[i]); Check Letter = BMJ_TABLE[Sum mod 29]
- 1. Multiply digits by weights [6, 5, 4, 3, 2, 1] aligned to the right.
- 2. Calculate remainder of sum modulo 29.
- 3. Lookup the check letter in the 29-letter BMJ table.
- 4. Ambiguous letters 'l' and 'o' are excluded.