# vat.py - functions for handling Irish VAT numbers # # Copyright (C) 2012-2016 Arthur de Jong # # This library is free software; you can redistribute it and/or # modify it under the terms of the GNU Lesser General Public # License as published by the Free Software Foundation; either # version 2.1 of the License, or (at your option) any later version. # # This library is distributed in the hope that it will be useful, # but WITHOUT ANY WARRANTY; without even the implied warranty of # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU # Lesser General Public License for more details. # # You should have received a copy of the GNU Lesser General Public # License along with this library; if not, write to the Free Software # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA # 02110-1301 USA """VAT (Irish tax reference number). The Irish VAT number consists of 8 or 9 digits. The number is either 7 digits and 1 letter (optionally followed by a W for married women), 7 digits and 2 letters, or 6 digits and 2 letters or symbols (in second and last position). >>> validate('IE 6433435F') # pre-2013 format '6433435F' >>> validate('IE 6433435OA') # 2013 format '6433435OA' >>> validate('6433435E') # incorrect check digit Traceback (most recent call last): ... InvalidChecksum: ... >>> validate('8D79739I') # old style number '8D79739I' >>> validate('8?79739J') # incorrect old style Traceback (most recent call last): ... InvalidFormat: ... >>> convert('1F23456T') '0234561T' """ from stdnum.exceptions import * from stdnum.util import clean def compact(number): """Convert the number to the minimal representation. This strips the number of any valid separators and removes surrounding whitespace.""" number = clean(number, ' -').upper().strip() if number.startswith('IE'): number = number[2:] return number _alphabet = 'WABCDEFGHIJKLMNOPQRSTUV' def calc_check_digit(number): """Calculate the check digit. The number passed should not have the check digit included.""" number = compact(number).zfill(7) return _alphabet[( sum((8 - i) * int(n) for i, n in enumerate(number[:7])) + 9 * _alphabet.index(number[7:])) % 23] def validate(number): """Checks to see if the number provided is a valid VAT number. This checks the length, formatting and check digit.""" number = compact(number) if not number[:1].isdigit() or not number[2:7].isdigit(): raise InvalidFormat() if not all(x in _alphabet for x in number[7:]): raise InvalidFormat() if len(number) not in (8, 9): raise InvalidLength() if number[:7].isdigit(): # new system (7 digits followed by 1 or 2 letters) if number[7] != calc_check_digit(number[:7] + number[8:]): raise InvalidChecksum() elif number[1] in 'ABCDEFGHIJKLMNOPQRSTUVWXYZ+*': # old system (second character is a letter or symbol) if number[7] != calc_check_digit(number[2:7] + number[0]): raise InvalidChecksum() else: raise InvalidFormat() return number def is_valid(number): """Checks to see if the number provided is a valid VAT number. This checks the length, formatting and check digit.""" try: return bool(validate(number)) except ValidationError: return False def convert(number): """Convert an "old" style 8-digit VAT number where the second character is a letter to the new 8-digit format where only the last digit is a character.""" number = compact(number) if len(number) == 8 and not number[1].isdigit(): number = '0' + number[2:7] + number[0] + number[7:] return number