Czech IČO Generator
Company and sole proprietor identification number in the Czech Republic (ARES).
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About Czech IČO
The Identifikační číslo osoby (IČO) is the mandatory 8-digit business identification number in the Czech Republic.
Managed by the Ministry of Finance via the ARES corporate database.
Anatomy & Structure of Czech IČO
The IČO consists of exactly 8 numeric digits:
| Position | Field | Length | Meaning | Example |
|---|---|---|---|---|
| 1 to 7 | Base Number | 7 digits | Sequential corporate identifier | 2559664 |
| 8 | Check Digit | 1 digit | Weighted Modulo 11 check digit | 1 |
Modulo 11 Algorithm for IČO
Official calculation rule used by ARES registry:
Sum = Σ(d[i] * (8 - i)); Remainder = Sum mod 11
- 1. Multiply the first 7 digits by weights [8, 7, 6, 5, 4, 3, 2].
- 2. Calculate remainder of sum divided by 11.
- 3. If remainder is 0 or 10, check digit is 1.
- 4. If remainder is 1, check digit is 0.
- 5. Otherwise, check digit is 11 - remainder.