The Geneva County Commission may, in its discretion, provide for the Tax Assessor and Tax Collector of Geneva County, a clerk hire allowance not to exceed seven thousand forty dollars ($7,040) for the period beginning August 1, 1979 and ending July 31, 1980; six thousand seven hundred dollars ($6,700) for the period beginning August 1, 1980 and ending July 31, 1981; and six thousand three hundred ninety-nine dollars ninety-six cents ($6,399.96) for the period beginning August 1, 1981 and ending July 31, 1982. Subsequent to August 1, 1982 such allowance shall not exceed six thousand dollars ($6,000) per annum which shall be paid when authorized by the Geneva County Commission from the county treasury in equal bimonthly installments on vouchers signed by officers entitled to the allowance. Such allowances shall be in lieu of all other allowances heretofore provided for such officers.