The heads of all departments, divisions or agencies of the city government, including the library department, and departments headed by commissions or elected officials shall submit to the mayor estimates of revenues and necessary expenditures for the ensuing fiscal year in such detail, in such form and at such time as the mayor shall prescribe.

The budget director shall assemble all estimates of revenues; necessary departmental expenditures; interest and redemption requirements for any city debt; and other pertinent budgetary information as may be required by uniform regulations of the state auditor; and, under the direction of the mayor, prepare a proposed budget for presentation to the city council.

The revenue estimates shall be based primarily on the collection experience of the first six months of the current fiscal year and the last six months of the preceding fiscal year and shall not include revenue from any source in excess of the amount so collected unless it shall be reasonably anticipated that such excess amounts will in fact be realized. The estimated revenues shall include sources previously established by law and unencumbered fund balances estimated to be available at the close of the current fiscal year. The estimated expenditures in the proposed budget shall, in no event, exceed such estimated revenues: PROVIDED, That the mayor may recommend expenditures exceeding the estimated revenues when accompanied by proposed legislation to raise at least an equivalent amount of additional revenue.

The mayor shall submit the proposed budget to the city council not later than ninety days prior to the beginning of the ensuing fiscal year.

The budget director shall cause sufficient copies of the proposed budget to be prepared and made available to all interested persons and shall cause a summary of the proposed budget to be published at least once in the city official newspaper.