Sec. 28.  Certain contracts and expenditures prohibited.
   No officer, department or agency shall, during any fiscal year, expend or contract to expend any money or incur any liability or enter into any contract which by its terms involves the expenditure of money on behalf of the Municipality for any purpose in excess of the amount appropriated and allotted for such expenditures or obligations. Any such obligation, oral or written, made in violation hereof shall be void. However, nothing in this section shall prevent the making of contracts not to be fully performed within the fiscal year when specifically authorized by the Council.