DIČ

Purpose

Use the dic detector for Czech VAT numbers (DIČ).

This detector reports accuracy above 98% and supports company, special, and individual forms.

Instead of using one standalone checksum rule, it validates the numeric payload against the matching Czech identifier format.

Detector Name

dic

Supported Formats

• CZ + 8 digits
• CZ + 9 digits
• CZ + 10 digits

The detector accepts input with or without the CZ prefix during validation.

Validation Logic

FastPII strips the CZ prefix if present, then applies length-based rules.

Company Form

• 8 digits
• Validated as an IČO
• Uses the IČO weighted MOD 11 checksum logic

Special Form

• 9 digits
• FastPII accepts the value only when the first digit is 6

Individual Form

• 10 digits
• Validated as a Czech birth number
• Uses the birth-number format and checksum logic

There is no separate DIČ-only checksum implementation in this detector.

Python Examples

Validate a company DIČ

from fastpii import PrivacyGuard

guard = PrivacyGuard(regions=["cz"])
result = guard.validate("CZ25596641", "dic")

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

Detect DIČ values in text

from fastpii import PrivacyGuard

guard = PrivacyGuard(regions=["cz"])
result = guard.detect("DIČ: CZ25596641", detector_names=["dic"])

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

Validate an individual DIČ

from fastpii import PrivacyGuard

guard = PrivacyGuard(regions=["cz"])
result = guard.validate("CZ8001011238", "dic")

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

Expected Metadata

This detector returns one metadata field:

• type: company, special, or individual

Example Output

{
    "type": "company",
}

Limitations

• Special 9-digit DIČ values are only checked by the leading 6 rule.
• The detector does not expose the nested IČO or birth-number metadata.
• Input outside the CZ + 8-10 digits range is rejected.

Notes

Verified validation example from the codebase:

guard.validate("CZ25596641", "dic")