csharp 计算含税，税额，不含税

Posted 2021-05-12

    /// <summary>
    /// 税计算扩展
    /// </summary>
    /// <remarks>
    ///  税额=含税/（1+税率%）*税率%
    ///  不含税=含税-税额
    /// （不含税计算时，不可用含税/（1+税率%），应优先计算税额，保留两位小数后，拿含税-税额=不含税）
    /// 
    ///  汇总类时只能汇总 含税、不含税、税额
    ///  税率 = 税额 /（含税-税额）
    /// </remarks>
    public static class TaxExtensions
    {
        /// <summary>
        /// 税额= 含税/（1+税率%）*税率%
        /// </summary>
        /// <param name="amount">含税</param>
        /// <param name="taxRatio">税率</param>
        /// <returns></returns>
        public static decimal CalcTaxAmount(this decimal amount, decimal taxRatio)
        {
            return Math.Round(amount / (1 + taxRatio / 100) * (taxRatio / 100), 2);
        }

        /// <summary>
        /// 计算税率
        /// </summary>
        /// <param name="amount">含税</param>
        /// <param name="taxAmount">税额</param>
        /// <returns></returns>
        public static decimal CalcTaxRatio(this decimal amount, decimal taxAmount)
        {
            var amountNoTax = amount - taxAmount;
            return amountNoTax == 0 ? 0 : Math.Round(taxAmount * 100 / amountNoTax, 2);
        }

        /// <summary>
        /// 计算不含税
        /// </summary>
        /// <param name="amount">含税</param>
        /// <param name="taxAmount">税额</param>
        /// <returns></returns>
        public static decimal CalcAmountNoTax(this decimal amount, decimal taxAmount)
        {
            return Math.Round(amount - taxAmount, 2);
        }
    }