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# pvn.py - functions for handling Latvian PVN (VAT) numbers
# coding: utf-8
#
# Copyright (C) 2012-2019 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
"""PVN (Pievienotās vērtības nodokļa, Latvian VAT number).
The PVN is a 11-digit number that can either be a reference to a legal
entity (in which case the first digit > 3) or a natural person (in which
case it should be the same as the personal code (personas kods)). Personal
codes start with 6 digits to denote the birth date in the form ddmmyy.
>>> validate('LV 4000 3521 600')
'40003521600'
>>> validate('40003521601') # invalid check digit
Traceback (most recent call last):
...
InvalidChecksum: ...
>>> validate('161175-19997') # personal code
'16117519997'
>>> validate('161375-19997') # invalid date
Traceback (most recent call last):
...
InvalidComponent: ...
"""
import datetime
from stdnum.exceptions import *
from stdnum.util import clean, isdigits
# validation functions are available on-line but it is not allowed
# to perform automated queries:
# https://www6.vid.gov.lv/VID_PDB?aspxerrorpath=/vid_pdb/pvn.asp
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('LV'):
number = number[2:]
return number
def checksum(number):
"""Calculate the checksum for legal entities."""
weights = (9, 1, 4, 8, 3, 10, 2, 5, 7, 6, 1)
return sum(w * int(n) for w, n in zip(weights, number)) % 11
def calc_check_digit_pers(number):
"""Calculate the check digit for personal codes. The number passed
should not have the check digit included."""
# note that this algorithm has not been confirmed by an independent source
weights = (10, 5, 8, 4, 2, 1, 6, 3, 7, 9)
check = 1 + sum(w * int(n) for w, n in zip(weights, number))
return str(check % 11 % 10)
def get_birth_date(number):
"""Split the date parts from the number and return the birth date."""
number = compact(number)
day = int(number[0:2])
month = int(number[2:4])
year = int(number[4:6])
year += 1800 + int(number[6]) * 100
try:
return datetime.date(year, month, day)
except ValueError:
raise InvalidComponent()
def validate(number):
"""Check if the number is a valid VAT number. This checks the length,
formatting and check digit."""
number = compact(number)
if not isdigits(number):
raise InvalidFormat()
if len(number) != 11:
raise InvalidLength()
if number[0] > '3':
# legal entity
if checksum(number) != 3:
raise InvalidChecksum()
else:
# natural resident, check if birth date is valid
get_birth_date(number)
# TODO: check that the birth date is not in the future
if calc_check_digit_pers(number[:-1]) != number[-1]:
raise InvalidChecksum()
return number
def is_valid(number):
"""Check if the number is a valid VAT number."""
try:
return bool(validate(number))
except ValidationError:
return False
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