Not later than thirty days prior to the beginning of the ensuing fiscal year the city council shall, by ordinance adopt the budget submitted by the mayor as modified by the city council.

The expenditure allowances as set forth in the enacted budget shall constitute the budget appropriations for the ensuing fiscal year. The city council by ordinance may, during the fiscal year covered by the enacted budget, abrogate or decrease any unexpended allowance contained within the budget and reappropriate such unexpended allowances for other functions or programs. Transfers between allowances in the budget of any department, division or agency may be made upon approval by the budget director pursuant to such regulations as may be prescribed by ordinance.