If the amount of tax computed by the Department is greater than the amount theretofore assessed, the excess shall be assessed by the Department and a bill for the same shall be mailed to the taxpayer. The taxpayer shall pay such additional tax to the Department within thirty days after the amount of the tax as computed is mailed by the Department. In such case, if the return was made in good faith and the understatement of the amount in the return was not due to any fault of the taxpayer, there shall be no penalty on the additional tax because of such understatement, but interest shall be added to the amount of the deficiency at a rate determined in accordance with § 58.1-15, from the time the return was required by law to be filed until paid. If the understatement is false or fraudulent with intent to evade the tax, a penalty of 100 percent shall be added together with interest on the tax at a rate determined in accordance with § 58.1-15, from the time the return was required by law to be filed until paid. Nothing contained in this section shall prevent the taxpayer from applying to the circuit court of the county or the city wherein he resides for a correction of the assessment made by the Department, with right of appeal in the manner provided by law.