In all counties in this state in which the county clerks are required by law to extend any improvement taxes, whether the taxes are from municipal, suburban, road, fire, drainage district, or otherwise, the county clerk of any such county shall receive, for his services in extending the tax annually upon the books of his county, a commission necessary to reimburse the clerk for the cost of extending the taxes. However, in no event may the commission exceed two percent (2%) of the amount so extended.