Whenever the county assessor discovers that any property has been omitted for any cause from the assessment roll, if it is before the county collector closes his or her books for the collection of taxes for the year in which the property was due to have been assessed, it shall be his or her duty, immediately upon making that discovery, to make a special list or assessment thereof and file it with the county clerk, who shall place it upon the tax books and extend the taxes and penalty thereon for the year. The county collector shall proceed to collect these taxes and penalty as is required by law.