93 lines
2.9 KiB
Python
93 lines
2.9 KiB
Python
# tin.py - functions for handling Ghana TIN numbers
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# coding: utf-8
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#
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# Copyright (C) 2022 Leandro Regueiro
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# Copyright (C) 2022 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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"""TIN (Taxpayer Identification Number, Ghana tax number).
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This number is issued by the Ghana Revenue Authority (GRA) to individuals who
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are not eligible for the Ghanacard PIN and other entities.
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This number consists of 11 alphanumeric characters. It begins with one of the
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following prefixes:
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P00 For Individuals.
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C00 For Companies limited by guarantee, shares, Unlimited (i.e organisation required to register with the RGD).
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G00 Government Agencies, MDAs.
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Q00 Foreign Missions, Employees of foreign missions.
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V00 Public Institutions, Trusts, Co-operatives, Foreign Shareholder (Offshore), (Entities not registered by RGD).
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More information:
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* https://www.oecd.org/tax/automatic-exchange/crs-implementation-and-assistance/tax-identification-numbers/Ghana-TIN.pdf
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* https://gra.gov.gh/tin/
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* https://gra.gov.gh/tin/tin-faq/
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>>> validate('C0000803561')
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'C0000803561'
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>>> validate('C0000803562')
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Traceback (most recent call last):
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...
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InvalidChecksum: ...
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""" # noqa: E501
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from __future__ import annotations
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import re
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from stdnum.exceptions import *
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from stdnum.util import clean
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_gh_tin_re = re.compile(r'^[PCGQV]{1}00[A-Z0-9]{8}$')
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def compact(number: str) -> str:
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"""Convert the number to the minimal representation.
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This strips the number of any valid separators and removes surrounding
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whitespace.
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"""
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return clean(number, ' ').upper()
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def calc_check_digit(number: str) -> str:
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"""Calculate the check digit for the TIN."""
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check = sum((i + 1) * int(n) for i, n in enumerate(number[1:10])) % 11
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return 'X' if check == 10 else str(check)
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def validate(number: str) -> str:
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"""Check if the number is a valid Ghana TIN."""
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number = compact(number)
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if len(number) != 11:
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raise InvalidLength()
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if not _gh_tin_re.match(number):
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raise InvalidFormat()
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if number[-1] != calc_check_digit(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 Ghana TIN."""
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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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