53 Pa. Stat. § 12551
On or before the fifteenth day of October of each year, the mayor shall furnish to the council, in such form and detail as the council shall have determined, a statement of the estimated receipts, other than from taxation, including money proposed to be borrowed and liabilities of every kind for the ensuing calendar year and the estimated expenditures for such year of all departments, officers, boards, commissions, trusts, committees, or other agencies, 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, designating which of such liabilities and expenditures should be met from current receipts and which should be met from loan funds. The estimates of receipts and liabilities shall be furnished to the mayor by the city controller. He shall also furnish to the mayor a statement of the borrowing capacity of the city. Such statements shall be made up by the city controller from the best available data, and the receipts from sources other than taxation and loans shall be estimated at the average of such receipts for the preceding three years, with due allowance for new sources of receipts not existing during all or part of said period of three years, for sources of receipts existing during all or part of said period which will not be available for the ensuing year, for changes in rates, and for other factors not previously existing. The estimates to be furnished by the city controller to the mayor, and by him transmitted to the council, shall also contain a statement of the average proportion of taxes uncollected at the end of each of the three preceding years. The estimated statement of expenditures shall be made up by the mayor from information supplied him by such departments, officers, boards, commissions, trusts, committees, and other agencies, subject to revision by the mayor in his discretion.
53 P.S. § 12551