The board shall establish the beginning and ending of its fiscal year, which period shall constitute its budget year, and at least thirty days prior to the beginning of the first full fiscal year after the creation of the district and annually thereafter the general manager shall prepare and submit to the board a tentative budget which shall include all operation and maintenance expenses, payments to a capital replacement account and bond payment schedules for the ensuing fiscal year. Such tentative budget shall be considered by the board, and, subject to any revisions or amendments that may be determined by the board, shall be adopted as the budget for the ensuing fiscal year. Upon adoption of the budget, a copy of the budget shall be forwarded to the county commission. No expenditures for operation and maintenance expenses in excess of the budget shall be made during such fiscal year unless unanimously authorized and directed by the board.