90 lines
3.1 KiB
Python
90 lines
3.1 KiB
Python
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# btw.py - functions for handling Dutch VAT numbers
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#
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# Copyright (C) 2012-2020 Arthur de Jong
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#
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# This library is free software; you can redistribute it and/or
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# modify it under the terms of the GNU Lesser General Public
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# License as published by the Free Software Foundation; either
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# version 2.1 of the License, or (at your option) any later version.
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#
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# This library is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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# Lesser General Public License for more details.
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#
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# You should have received a copy of the GNU Lesser General Public
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# License along with this library; if not, write to the Free Software
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# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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# 02110-1301 USA
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"""Btw-identificatienummer (Omzetbelastingnummer, the Dutch VAT number).
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The btw-identificatienummer (previously the btw-nummer) is the Dutch number
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for identifying parties in a transaction for which VAT is due. The btw-nummer
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is used in communication with the tax agency while the
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btw-identificatienummer (EORI-nummer) can be used when dealing with other
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companies though they are used interchangeably.
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The btw-nummer consists of a RSIN or BSN followed by the letter B and two
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digits that identify the number of the company created. The
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btw-identificatienummer has a similar format but different checksum and does
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not contain the BSN.
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More information:
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* https://en.wikipedia.org/wiki/VAT_identification_number
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* https://nl.wikipedia.org/wiki/Btw-nummer_(Nederland)
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>>> validate('004495445B01')
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'004495445B01'
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>>> validate('NL4495445B01')
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'004495445B01'
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>>> validate('NL002455799B11') # valid since 2020-01-01
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'002455799B11'
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>>> validate('123456789B90')
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Traceback (most recent call last):
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...
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InvalidChecksum: ...
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"""
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from __future__ import annotations
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from stdnum.exceptions import *
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from stdnum.iso7064 import mod_97_10
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from stdnum.nl import bsn
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from stdnum.util import clean, isdigits
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def compact(number: str) -> str:
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"""Convert the number to the minimal representation. This strips the
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number of any valid separators and removes surrounding whitespace."""
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number = clean(number, ' -.').upper().strip()
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if number.startswith('NL'):
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number = number[2:]
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return bsn.compact(number[:-3]) + number[-3:]
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def validate(number: str) -> str:
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"""Check if the number is a valid btw number. This checks the length,
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formatting and check digit."""
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number = compact(number)
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if not isdigits(number[:9]) or int(number[:9]) <= 0:
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raise InvalidFormat()
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if not isdigits(number[10:]) or int(number[10:]) <= 0:
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raise InvalidFormat()
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if len(number) != 12:
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raise InvalidLength()
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if number[9] != 'B':
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raise InvalidFormat()
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if not bsn.is_valid(number[:9]) and not mod_97_10.is_valid('NL' + number):
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raise InvalidChecksum()
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return number
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def is_valid(number: str) -> bool:
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"""Check if the number is a valid btw number."""
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try:
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return bool(validate(number))
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except ValidationError:
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return False
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