During the session of the council sitting as a board of equalization, it may direct the assessor to assess any taxable property that has escaped assessment, or to add to the amount, number or quantity of property when a false or incomplete list has been rendered; and to make and enter new assessments (at the same time canceling previous entries) when any assessment made by him is deemed by the council so incomplete as to render doubtful the collection of the tax; but the clerk must notify all persons interested by letter delivered personally or deposited in the post office, postage prepaid, and addressed to the person interested, a reasonable time before action taken, of the day fixed when the matter will be investigated. (Prior code § 6.04.410)