税

zei.py

# 2018年度用

def calc_kojin(income, age):
    # 基礎控除
    kisokoujyo_kuni = 38
    kisokoujyo_chihou = 33

    # 給与所得控除 https://www.nta.go.jp/m/taxanswer/1410.htm
    if income <= 180:
        kyuyo_shotoku_koujyo = max(65, income * 0.4)
    elif income <= 360:
        kyuyo_shotoku_koujyo = income * 0.3 + 18
    elif income <= 660:
        kyuyo_shotoku_koujyo = income * 0.2 + 54
    elif income <= 1000:
        kyuyo_shotoku_koujyo = income * 0.1 + 120
    else:
        kyuyo_shotoku_koujyo = 220

    # 厚生年金 https://www.kyoukaikenpo.or.jp/~/media/Files/shared/hokenryouritu/h30/ippan4gatu_2/h30413tokyo_02.pdf
    if income <= 9.3 * 12:
        kousei_nenkin = 1.6104 * 12
    elif income <= 63.5 * 12:
        kousei_nenkin = income * 0.183
    else:
        kousei_nenkin = 11.346 * 12

    # 協会けんぽ
    if 40 <= age <= 64:
        if income <= 6.3 * 12:
            kenpo = 0.5742 * 12
        elif income <= 135.5 * 12:
            kenpo = income * 0.1147
        else:
            kenpo = 15.9433 * 12
    else:
        if income <= 6.3 * 12:
            kenpo = 0.66526 * 12
        elif income <= 135.5 * 12:
            kenpo = income * 0.099
        else:
            kenpo = 13.7610 * 12

    # 所得税 https://www.nta.go.jp/taxes/shiraberu/taxanswer/shotoku/2260.htm
    kazei_income_kuni = max(0,
                            income - kisokoujyo_kuni -
                            kyuyo_shotoku_koujyo - (kousei_nenkin + kenpo) / 2)
    if kazei_income_kuni <= 195:
        syotokuzei = kazei_income_kuni * 0.05
    elif kazei_income_kuni <= 330:
        syotokuzei = kazei_income_kuni * 0.1 - 9.75
    elif kazei_income_kuni <= 695:
        syotokuzei = kazei_income_kuni * 0.2 - 42.75
    elif kazei_income_kuni <= 900:
        syotokuzei = kazei_income_kuni * 0.23 - 63.6
    elif kazei_income_kuni <= 1800:
        syotokuzei = kazei_income_kuni * 0.33 - 153.6
    elif kazei_income_kuni <= 4000:
        syotokuzei = kazei_income_kuni * 0.4 - 279.6
    else:
        syotokuzei = kazei_income_kuni * 0.45 - 479.6
    # 特別復興所得税
    syotokuzei = syotokuzei * 1.021

    # 住民税
    kazei_income_chihou = max(0,
                              income - kisokoujyo_chihou - \
                              kyuyo_shotoku_koujyo - (kousei_nenkin + kenpo) / 2)
    jyuminzei = kazei_income_chihou * 0.1

    zei = syotokuzei + jyuminzei + kenpo
    # print("%d\t%f" % (income, zei / income))
    return zei, (kousei_nenkin + kenpo) / 2


def calc_houjin(income):
    # 法人税
    houjinzei = min(800, income) * 0.15 + max(0, income - 800) * 0.232
    # 地方法人税
    chihou_houjinzei = houjinzei * 0.044
    # 法人住民税
    houjin_jyuminzei = houjinzei * 0.129 if houjinzei <= 1000 else houjinzei * 0.163
    # 法人事業税
    if income <= 2500:
        houjin_jigyouzei = min(400, income) * 0.034 + \
                           max(0, min(400, income - 400)) * 0.051 + \
                           max(0, income - 800) * 0.067
    else:
        houjin_jigyouzei = min(400, income) * 0.0365 + \
                           max(0, min(400, income - 400)) * 0.05465 + \
                           max(0, income - 800) * 0.0718
    # 地方法人特別税
    houjin_toubetsuzei = houjin_jigyouzei * 0.432

    hyoumen_zeigaku = houjinzei + chihou_houjinzei + houjin_jyuminzei + houjin_jigyouzei + houjin_toubetsuzei
    jikkou_zeiritsu = hyoumen_zeigaku / (income + houjin_jigyouzei + houjin_toubetsuzei)

    hyoumen_zeigaku_kintouwari = hyoumen_zeigaku + 7
    jikkou_zeiritsu_kintouwari = hyoumen_zeigaku_kintouwari / (income + houjin_jigyouzei + houjin_toubetsuzei)

    # print("法人税 = %f" % houjinzei)
    # print("地方法人税 = %f" % chihou_houjinzei)
    # print("法人住民税 = %f" % houjin_jyuminzei)
    # print("法人事業税 = %f" % houjin_jigyouzei)
    # print("地方法人特別税 = %f" % houjin_toubetsuzei)
    # print("表面税額(-均等割) = %f" % hyoumen_zeigaku)
    # print("実効税率(-均等割) = %f" % (jikkou_zeiritsu * 100))
    # print("表面税額(+均等割) = %f" % hyoumen_zeigaku_kintouwari)
    # print("実効税率(+均等割) = %f" % (jikkou_zeiritsu_kintouwari * 100))
    # print("%d\t%f" % (income, jikkou_zeiritsu))
    # print("%d\t%f" % (income, jikkou_zeiritsu_kintouwari))

    return income * jikkou_zeiritsu


def find_best(income, age):
    best_zei_total = 1e100
    best_kojin_income = 0

    # for kojin_income in range(80, income + 10, 10):
    for kojin_income in range(80, 1300, 1):
        zei_kojin, koujyo = calc_kojin(kojin_income, age)
        if income > kojin_income + koujyo:
            zei_houjin = calc_houjin(income - kojin_income - koujyo)
        else:
            zei_houjin = 0
        zei_total = zei_kojin + zei_houjin
        # print("%d\t%d\t%d\t%d\t%d" % (kojin_income, zei_kojin, koujyo, zei_houjin, zei_total))
        if zei_total <= best_zei_total:
            best_zei_total = zei_total
            best_kojin_income = kojin_income

    print("%d\t%d" % (income, best_kojin_income))


def main():
    for income in range(80, 5010, 10):
        find_best(income, 39)
        # calc_houjin(income)
        # calc_kojin(income, 39)


main()