Slovenia (SI)

Slovenian VAT Number Validation

Format, pattern, and MOD 11 checksum algorithm for SI VAT numbers

Slovenian VAT numbers (Identifikacijska številka za DDV) consist of 8 digits with a weighted MOD 11 checksum.

Format vs. Active Validation

This checks format only, not if a VAT number is really registered. Use VatDB's API to verify is a number is really registered and active. VatDB checks official EU and national datasources.

Format Overview

Property Value
Country Code SI
Format 8 digits
Length 8 digits
Example SI12345678

Regex Pattern

^SI[0-9]{8}$

Checksum Algorithm (MOD 11)

def validate_si_vat(number):
    if number.startswith('SI'):
        number = number[2:]

    if len(number) != 8 or not number.isdigit():
        return False

    weights = [8, 7, 6, 5, 4, 3, 2]
    total = sum(int(d) * w for d, w in zip(number[:7], weights))
    check = 11 - (total % 11)

    if check == 10:
        return False  # Invalid number
    if check == 11:
        check = 0

    return check == int(number[7])

Note: If the check calculation results in 10, the VAT number is invalid.

Frequently Asked Questions

How do I verify a Slovenian VAT number?
Slovenian VAT numbers use weighted MOD 11 with weights [8,7,6,5,4,3,2]. If check=10, invalid. If check=11, check digit is 0. Use VatDB's API for official verification against EU and national databases.
What does a Slovenian VAT number look like?
A Slovenian VAT number has the format SI12345678 - 'SI' followed by exactly 8 digits. The last digit is the check digit.
How many digits are in a Slovenian VAT number?
A Slovenian VAT number contains exactly 8 digits after the SI country code. The complete number is 10 characters: SI + 8 digits.
What happens if the Slovenian VAT checksum equals 10?
If the MOD 11 check calculation results in 10, the VAT number is invalid. This ensures all valid Slovenian VAT numbers have single-digit check values (0-9).
Where can I check a Slovenian company's VAT number?
Use VatDB's API to validate VAT numbers against official EU and national databases. Get instant verification with company information.
What's the difference between format validation and checking if a VAT number is active?
Format validation proves the number is properly structured, not that it's registered. Businesses close, VAT registrations get revoked. VatDB verifies the number is genuinely active.

Validate Slovenian VAT Numbers Instantly

Use our API for real-time SI VAT number validation

Try Free