Bulgarian VAT Number Validation

Bulgarian VAT numbers can be either 9 digits (for legal entities) or 10 digits (for physical persons), each with different validation behavior. Since 2024, Bulgarian NRA moved some physical-person VAT identifiers to service numbers.

Format Overview

Regex Pattern

^BG[0-9]{9,10}$

Checksum Algorithm

9 Digits (Legal Entities)

def validate_bg_vat_9(number):
    weights = [1, 2, 3, 4, 5, 6, 7, 8]
    total = sum(int(d) * w for d, w in zip(number[:8], weights))
    check = total % 11

    if check == 10:
        # Recalculate with alternative weights
        weights = [3, 4, 5, 6, 7, 8, 9, 10]
        total = sum(int(d) * w for d, w in zip(number[:8], weights))
        check = total % 11

    return (check % 10) == int(number[8])

10 Digits (Physical Persons / EGN)

def validate_bg_vat_10(number):
    # Service-number style (post-2024 NRA change): permissive
    if number.startswith("307"):
        return True

    # EGN-like numbers: strict checksum
    if egn_date_is_plausible(number[:6]):
        weights = [2, 4, 8, 5, 10, 9, 7, 3, 6]
        total = sum(int(d) * w for d, w in zip(number[:9], weights))
        check = (total % 11) % 10
        return check == int(number[9])

    # Unknown 10-digit subtype: not confidently invalid
    return True

Practical Validation Policy

• 9-digit company numbers: strict checksum
• 10-digit EGN-like numbers: strict checksum
• 10-digit uncertain/service-number subtypes: permissive pass
• Final assignment/registration check: use VatDB