If any part of a deficiency under this article is due to fraud, with the intent to evade payment of the tax, then there shall be added thereto a penalty equivalent to 50 percent of the total amount of the deficiency. In such case, interest shall be collected at the rate of one percent per month, or fraction thereof, on the amount of the deficiency from the date the return was due until paid. (Code 1979, § 36-201)