53 Pa. Stat. § 12554
The council may, from time to time, make appropriations out of such estimated receipts of the city for the ensuing year to meet the requirements of such departments, officers, boards, commissions, trusts, committees, and other agencies, as determined by the council, but from the receipts of the city from taxation and sources, other than loan funds, estimated as provided in this article, the council shall appropriate, before the beginning of the ensuing year, a sufficient amount for the extinguishment of the floating indebtedness (other than that accruing within one year from condemnation of real property) which the city controller may estimate to be outstanding upon the first of January following, for the payment of all lawful obligations due by the city during the fiscal year commencing January first, and for such expenditures to be met from such receipts as may be authorized by the council; and the city controller shall not countersign any warrants (except for payment of interest and for sinking-fund) pertaining to any of the appropriations until the said council shall have first passed all appropriations necessary for the expenses for the current year of each department, officer, board, commission, trust, committee or other agency whose financial requirements are to be met out of the proceeds of taxes levied by the council or out of any other funds over which the council has control, nor shall said officer countersign any warrants, except as aforesaid, until the total of all appropriations and all lawful obligations (other than as aforesaid), as estimated by the city controller, shall have been brought within the sum of the estimated receipts from taxes and from other sources except loan funds. No contract shall be binding upon the city unless an appropriation therefor has previously been made (except as otherwise provided in this act); and no warrant shall be drawn, issued, or approved by any officer of said city for any expenditure by such department, officer, board, commission, trust, committee, or other agency, unless an appropriation has previously been made in accordance with the provisions of this act; and no warrant shall be drawn against any item in said appropriation in excess of said item; and any contract made or warrant issued in violation of this article shall be absolutely void. Any appropriation in violation of this article or in excess of the estimated receipts as set forth in said ordinance and any contract based thereon shall be void: Provided, however, That the council shall have the power to appropriate money received in excess of said estimate, upon the certificate of the city controller that there have been such excess receipts: And provided further, That surplus receipts, if any, carried over from one year into the next may be appropriated during the next said year, in addition to the appropriation of the said estimated receipts for that year. Said appropriations, if within the limits aforesaid, shall be valid, and contracts may be lawfully based thereon, although the money estimated to be received during the said year shall not actually have been received or be in the treasury at the time of said appropriation or contract: And provided further, That the council may by ordinance make transfers from one item of appropriation to another.
53 P.S. § 12554