If the Commission ascertains that any assessment that could have been assessed during any current assessable year has not been assessed for any assessable year of the three years last past, or that the same has been assessed at less than the law required for any one or more of such years, or that the assessment, for any cause, has not been realized, the Commission shall list and assess the same at the rate prescribed for that year, adding thereto a penalty of 10 percent and interest at the rate established pursuant to § 58.1-1812 which shall be computed upon the assessment from the due date of the assessment until the assessment is paid.