If the county auditor shall at any time discover that any real estate or new structure, duly returned and appraised for taxation, has been omitted from the duplicate, he shall immediately charge it on the duplicate with the taxes of the current year and the simple taxes of each preceding year it may have escaped taxation. And if the owner of any real estate or new structure thereon, subject to taxation, has not reported it for taxation, according to the requirements of this chapter, and it has not been appraised for taxation, the auditor shall, upon discovery thereof, appraise it and, upon making return of such appraisement, shall charge it upon the duplicate, with the taxes of the then current year and the taxes of each preceding year it may have escaped taxation, with twenty per cent penalty upon such taxes of preceding years. And if any real estate shall have been omitted in any return, the auditor of the county shall appraise it immediately for taxation, file such appraisement in his office and charge it with the taxes of the current year and the simple taxes of preceding years it may have escaped taxation.