The amount of compensation to be charged and paid to the county of San Diego for the performance of the services of assessing and collecting taxes for the City shall be fixed by agreement between the Board of Supervisors of San Diego County and the Council; provided, however, that not more than one percent be charged for collecting the first $25,000 so collected and not more than one-fourth of one percent for all sums over that amount. The auditor of the county is hereby authorized to deduct such compensation from taxes collected under this chapter. (Prior code § 30.3).