If, upon examination of any returns or from other information obtained by the city treasurer, it appears that a tax or penalty has been paid less than that properly due, the treasurer shall assess against the taxpayer such additional amount found to be due and shall add thereto interest at the rate of six percent per year from the last day of the period in which the deficiency is incurred until date of payment. The treasurer shall notify the taxpayer by mail of the additional amount, and the same shall become due and shall be paid within 10 days from the date of the notice. If payment is not received by the treasurer by the due date specified in the notice, the treasurer shall add a penalty of 10 percent of the amount of the additional tax found due.

No assessment or correction of an assessment for additional taxes due may be made by the treasurer more than four years after the close of the tax year, except upon a showing of fraud or of misrepresentation of a material fact by the taxpayer, or where a taxpayer has executed a written waiver of such limitation. (Ord. 814 § 9, 1976).