(a) The board shall prepare and approve an annual budget.
(b) The budget must contain a complete financial statement, including a statement of:
(1) the outstanding obligations of the district;
(2) the amount of cash credited to each district fund;
(3) the amount of money the district received from all sources during the previous year;
(4) the amount of money available to the district from all sources during the ensuing year;
(5) the balances expected at the end of the year in which the budget is being prepared;
(6) the estimated revenue and balances available to cover the proposed budget; and
(7) the estimated tax rate that will be required.

(c) The board may amend the budget after adoption.
(d) Money may not be spent for an expense not included in the budget or an amendment to it unless the board by order declares the expense to be necessary.