No contract, agreement, or other obligation involving the expenditure of money, shall be entered into, nor shall any ordinance, resolution or order for the expenditure of money be issued by the Council or be authorized by any officer of the City unless the Director of Finance shall have first certified in writing to the Council, or to the proper officer, as the case may be, that the money required for such contract, agreement, obligation, or expenditure, is in the treasury to the credit of the fund from which it is to be drawn, and not appropriated for any other purpose, which certificate shall be filed and immediately recorded. The sum so certified shall not thereafter be considered unappropriated until the City is discharged from the contract, agreement, or obligation; but the provisions of this section shall not be construed as prohibiting the making of contracts for the furnishing of services or public utilities for a period extending beyond a single fiscal year when such contracts are otherwise authorized by this Charter or by general law.