The revenue commissioner shall combine all budgetary operations and functions of the office of the revenue commissioner that were previously divided into the budgetary operations and functions of the tax assessor and the budgetary operations and functions of the tax collector. The expenses of the office shall be financed on a pro rata basis and allocated in the same manner that the salary of the revenue commissioner is paid pursuant to Section 40-6A-2. Any funds retained as a result of the combining of budgetary operations and functions pursuant to this section shall be used solely for the operation of the office of the revenue commissioner subject to approval of the budget for the office by the county commission in the same manner as the budget is currently approved.