Who cares about Domain Rules?

namespace BusinessRules.Evolution_Two
{
    /// <summary>
    /// Investor Domain object specific to New Zealand
    /// </summary>
    internal class NewZealandInvestor : Investor
    {
        #region Fiels

        private double taxRate;

        #endregion

        #region C'tors

        /// <summary>
        /// Initializes a new instance of the <see cref="NewZealandInvestor"/> class.
        /// </summary>
        /// <param name="income">The income.</param>
        internal NewZealandInvestor(double income) : base(income)
        {
        }

        #endregion

        #region Properties

        /// <summary>
        /// Gets the tax rate.
        /// </summary>
        /// <value>The tax rate.</value>
        public override double TaxRate
        {
            get
            {
                double inv_income = Income;

                if (inv_income >= 0.0 && inv_income <= 19500.99)
                    taxRate = 0.195;
                else if (inv_income >= 19501.00 && inv_income <= 60000.99)
                    taxRate = 0.33;
                else
                    taxRate = 0.39;

                return taxRate;
            }
        }

        /// <summary>
        /// Gets the tax liability.
        /// </summary>
        /// <value>The tax liability.</value>
        public override double TaxLiability
        {
            get
            {
                double taxLiability = 0.0;
                double inv_income = Income;
                if (inv_income > 19500.99)
                {
                    taxLiability += 19500.99 * 0.195;
                }
                if (inv_income <= 19500.99)
                {
                    taxLiability += inv_income * 0.195;
                }
                if (inv_income > 60000.99)
                {
                    taxLiability += (60000.99 - 19501.00) * 0.33;
                }
                if (inv_income >= 19501.00 && inv_income <= 60000.99)
                {
                    taxLiability += (inv_income - 19501.00) * 0.33;
                }
                if (inv_income > 60000.99)
                {
                    taxLiability += (inv_income - 60000.99) * 0.39;
                }

                return taxLiability;
            }
        }

        #endregion
    }
}