The commissioners in counties of the third to eighth classes may at any time, by resolution, make supplemental appropriations for any lawful purpose from any funds on hand or estimated to be received within the fiscal year and not otherwise appropriated, including the proceeds of any borrowing now or hereafter authorized by law. The commissioners may authorize the transfer of any unencumbered balance of any appropriation item or any portion thereof. During the last fifteen days of any fiscal year, the county commissioners shall have the power to authorize the transfer of any unencumbered balance, or any portion thereof, from any institution district fund to any county fund, and to reappropriate such moneys to the county.

No work shall be hired to be done, no materials purchased, no contracts made, and no order issued for the payment of any moneys by the commissioners, which will cause the sums appropriated to be exceeded.