IČO

Purpose

Use the ico detector for Czech company identification numbers (IČO).

This detector is built for 8-digit business IDs and reports accuracy above 99%.

It validates the official weighted checksum and exposes whether the checksum passed.

Detector Name

ico

Supported Formats

• 8 digits

Examples:

• 25596641
• 00000019

The validator removes spaces before checking the value.

Validation Logic

The detector requires exactly 8 digits.

It then validates the last digit using a weighted MOD 11 algorithm.

Checksum Algorithm

1. Take the first 7 digits.
2. Multiply them by weights 8, 7, 6, 5, 4, 3, 2.
3. Sum the products.
4. Compute sum % 11.
5. Map the remainder to the expected check digit:
   • remainder 0 -> check digit 1
   • remainder 1 -> check digit 0
   • remainder 2-10 -> 11 - remainder
6. Compare the expected check digit with the 8th digit.

Python Examples

Validate an IČO

from fastpii import PrivacyGuard

guard = PrivacyGuard(regions=["cz"])
result = guard.validate("25596641", "ico")

print(result.is_valid)
print(result.metadata)

Detect an IČO in text

from fastpii import PrivacyGuard

guard = PrivacyGuard(regions=["cz"])
result = guard.detect("IČO: 25596641", detector_names=["ico"])

for finding in result.findings:
    print(finding.value, finding.metadata)

Expected Metadata

This detector returns:

• checksum_valid

Example Output

{
    "checksum_valid": True,
}

Limitations

• FastPII expects the business ID itself, not a prefixed form like CZ25596641.
• Values longer than 8 digits are rejected.
• The detector does not add company registry enrichment.

Notes

Verified validation example from the codebase:

guard.validate("25596641", "ico")