53 Pa. Stat. § 12553
On or before the same date, the council shall levy and fix a tax rate for the ensuing year, which, together with the estimated receipts from all other sources except borrowed money, shall yield sufficient receipts to meet the liabilities of the city of every kind (except liabilities to be paid out of loan funds) for the ensuing year and the current expenditures, not including expenditures from loan funds, as fixed and determined by the council in said ordinance. The receipts from taxation shall be estimated by deducting, from the gross amount which would be yielded at the rate fixed, the average proportion of the amount uncollected at the end of each year during the preceding three years. If the council shall fail to fix a tax rate on or before the fifteenth day of December of any year, the rate for the current year shall be the rate for the ensuing year as if that rate had been fixed by the council in accordance with this act, and the amount of expenditures, other than from loan funds, shall be fixed and determined by the council so as to come within the estimated receipts from sources other than loans.
53 P.S. § 12553