前言
使用此种计算方式前,需要知道当年已纳税总额度以及本月应纳税额度。这两个参数需要自行根据各自系统数据计算出来,此方法只实现个税计算算法。此外,需要打开PHP的bc扩展。
参数
方法传入两个参数即可,当月应纳税额度以及本年已纳税总额度(不含当月)。
- $lauwen_monthly_tax_amount:当月应纳税额度。
- $lauwen_taxed_amount:当年已纳税总额度(不含当月)。
实现
首先是确认两个层级,一个是本年已纳税总额度所在税率层级(不含当月),另一个是本月之后本年已纳税总额度所在税率层级(含当月);最后在计算个税时使用了两种计算方式,一种是分别计算在每个税率层级的税额;另一种是使用速算扣除数进行计算,按需使用就好。
分级计算核心代码
// 分级法计算
$tax = '0';
while ($new_key >= $old_key) {
$level_amount = bcsub($lauwen_month_after_amount, $lauwen_tax_amounts[$new_key], 6);
if ($new_key == $old_key) {
$level_amount = bcsub($lauwen_month_after_amount, $lauwen_taxed_amount, 6);
}
$tax = bcadd($tax, bcmul($level_amount, $lauwen_tax_rates[$new_key]), 2);
$lauwen_month_after_amount = $lauwen_tax_amounts[$new_key];
$new_key --;
}
速算扣除计算核心代码
// 速算扣除法计算
$quickly_old_tax = bcsub(bcmul($lauwen_taxed_amount, $lauwen_tax_rates[$old_key], 6), $lauwen_tax_quickly[$old_key], 6);
$quickly_new_tax = bcsub(bcmul($lauwen_month_after_amount, $lauwen_tax_rates[$new_key], 6), $lauwen_tax_quickly[$new_key], 6);
$tax0 = bcsub($quickly_new_tax, $quickly_old_tax, 2);
全部代码
function personTax($lauwen_monthly_tax_amount, $lauwen_taxed_amount) {
$lauwen_tax_amounts = ['0', '36000', '144000', '300000', '420000', '660000', '960000'];
$lauwen_tax_rates = ['0.03', '0.1', '0.2', '0.25', '0.3', '0.35', '0.45'];
$lauwen_tax_quickly = ['0', '2520', '16920', '31920', '52920', '85920', '181920'];
$lauwen_taxed_amount = (string)$lauwen_taxed_amount;
$lauwen_monthly_tax_amount = (string)$lauwen_monthly_tax_amount;
$lauwen_month_after_amount = bcadd($lauwen_taxed_amount, $lauwen_monthly_tax_amount, 6);
// 确定当月前当年已纳税总额度所属级别,以及当月之后当年已纳税总额度所属级别
$old_key = 0; // 当月前级别
$new_key = 0; // 当月后级别
$end_key = count($lauwen_tax_amounts) - 1;
foreach ($lauwen_tax_amounts as $key => $val) {
if ($key == $end_key) { // 最后一级
if (bccomp($lauwen_taxed_amount, $val, 2) == 1) {
$old_key = $key;
}
if (bccomp($lauwen_month_after_amount, $val, 2) == 1) {
$new_key = $key;
}
} else { //
if (bccomp($lauwen_taxed_amount, $val, 2) == 1 && bccomp($lauwen_taxed_amount, $lauwen_tax_amounts[$key+1], 2) == -1) {
$old_key = $key;
}
if (bccomp($lauwen_month_after_amount, $val, 2) == 1 && bccomp($lauwen_month_after_amount, $lauwen_tax_amounts[$key+1], 2) == -1) {
$new_key = $key;
break;
}
}
}
// 速算扣除法计算
$quickly_old_tax = bcsub(bcmul($lauwen_taxed_amount, $lauwen_tax_rates[$old_key], 6), $lauwen_tax_quickly[$old_key], 6);
$quickly_new_tax = bcsub(bcmul($lauwen_month_after_amount, $lauwen_tax_rates[$new_key], 6), $lauwen_tax_quickly[$new_key], 6);
$tax0 = bcsub($quickly_new_tax, $quickly_old_tax, 2);
// 差额法计算
$tax = '0';
while ($new_key >= $old_key) {
$level_amount = bcsub($lauwen_month_after_amount, $lauwen_tax_amounts[$new_key], 6);
if ($new_key == $old_key) {
$level_amount = bcsub($lauwen_month_after_amount, $lauwen_taxed_amount, 6);
}
$tax = bcadd($tax, bcmul($level_amount, $lauwen_tax_rates[$new_key]), 2);
$lauwen_month_after_amount = $lauwen_tax_amounts[$new_key];
$new_key --;
}
return json_encode([
"normal" => $tax,
"quickly" => $tax0,
]);
}