Inclusive Taiwan Identification Number Validation

"""Taiwan ID number validator.

Accepts ROC national ID numbers, legacy ARC/APRC numbers (two leading
letters, issued before 2021) and new-format ARC/APRC numbers (letter + 8/9,
issued from 2021).

Format: 1 letter, then 1/2 (citizen), A-D (legacy ARC) or 8/9 (new ARC),
then 7 digits and a check digit.
"""
import re

ID_PATTERN = re.compile(r'[A-Z][12A-D89][0-9]{8}')
LETTER_CODES = 'ABCDEFGHJKLMNPQRSTUVXYWZIO'  # index + 10 = the letter's numeric code


def is_valid(id_number):
    normalized = str(id_number).upper()
    if not ID_PATTERN.fullmatch(normalized):
        return False

    letter_code = LETTER_CODES.index(normalized[0]) + 10
    total = letter_code // 10 + (letter_code % 10) * 9

    # A letter in the second position (legacy ARC) counts as the last digit of its code.
    second = normalized[1]
    if second.isalpha():
        second_value = (LETTER_CODES.index(second) + 10) % 10
    else:
        second_value = int(second)
    total += second_value * 8

    for position in range(2, 9):
        total += (9 - position) * int(normalized[position])
    total += int(normalized[9])

    return total % 10 == 0

<?php
// Taiwan ID number validator.
//
// Accepts ROC national ID numbers, legacy ARC/APRC numbers (two leading
// letters, issued before 2021) and new-format ARC/APRC numbers (letter + 8/9,
// issued from 2021).
//
// Format: 1 letter, then 1/2 (citizen), A-D (legacy ARC) or 8/9 (new ARC),
// then 7 digits and a check digit.

const TAIWAN_ID_PATTERN = '/^[A-Z][12A-D89][0-9]{8}\z/';
const TAIWAN_ID_LETTER_CODES = 'ABCDEFGHJKLMNPQRSTUVXYWZIO'; // index + 10 = the letter's numeric code

function isValid(string $idNumber): bool
{
    $normalized = strtoupper($idNumber);
    if (preg_match(TAIWAN_ID_PATTERN, $normalized) !== 1) {
        return false;
    }

    $letterCode = strpos(TAIWAN_ID_LETTER_CODES, $normalized[0]) + 10;
    $sum = intdiv($letterCode, 10) + ($letterCode % 10) * 9;

    // A letter in the second position (legacy ARC) counts as the last digit of its code.
    $second = $normalized[1];
    $secondValue = ctype_alpha($second)
        ? (strpos(TAIWAN_ID_LETTER_CODES, $second) + 10) % 10
        : (int) $second;
    $sum += $secondValue * 8;

    for ($i = 2; $i < 9; $i++) {
        $sum += (9 - $i) * (int) $normalized[$i];
    }
    $sum += (int) $normalized[9];

    return $sum % 10 === 0;
}

Coming soon

import java.util.Locale;

/**
 * Taiwan ID number validator.
 *
 * Accepts ROC national ID numbers, legacy ARC/APRC numbers (two leading
 * letters, issued before 2021) and new-format ARC/APRC numbers (letter + 8/9,
 * issued from 2021).
 *
 * Format: 1 letter, then 1/2 (citizen), A-D (legacy ARC) or 8/9 (new ARC),
 * then 7 digits and a check digit.
 */
public final class TaiwanId {

    private static final String ID_PATTERN = "[A-Z][12A-D89][0-9]{8}";
    private static final String LETTER_CODES = "ABCDEFGHJKLMNPQRSTUVXYWZIO"; // index + 10 = the letter's numeric code

    private TaiwanId() {}

    public static boolean isValid(String idNumber) {
        if (idNumber == null) {
            return false;
        }
        String normalized = idNumber.toUpperCase(Locale.ROOT);
        if (!normalized.matches(ID_PATTERN)) {
            return false;
        }

        int letterCode = LETTER_CODES.indexOf(normalized.charAt(0)) + 10;
        int sum = letterCode / 10 + (letterCode % 10) * 9;

        // A letter in the second position (legacy ARC) counts as the last digit of its code.
        char second = normalized.charAt(1);
        int secondValue = Character.isLetter(second)
            ? (LETTER_CODES.indexOf(second) + 10) % 10
            : second - '0';
        sum += secondValue * 8;

        for (int i = 2; i < 9; i++) {
            sum += (9 - i) * (normalized.charAt(i) - '0');
        }
        sum += normalized.charAt(9) - '0';

        return sum % 10 == 0;
    }
}