On or before the second Monday of the fourth month prior to the beginning of the city’s or town’s next fiscal biennium, or at such other time as the city or town may provide by ordinance or charter, the clerk shall notify in writing the head of each department of a city or town to file with the clerk within fourteen days of the receipt of such notification, detailed estimates of the probable revenue from sources other than ad valorem taxation and of all expenditures required by the department for the ensuing fiscal biennium. The notice shall be accompanied by the proper forms provided by the clerk, prepared in accordance with the requirements and classification established by the state auditor. The clerk shall prepare the estimates for interest and debt redemption requirements and all other estimates, the preparation of which falls properly within the duties of the clerk’s office. The chief administrative officers of the city or town shall submit to the clerk detailed estimates of all expenditures proposed to be financed from the proceeds of bonds or warrants not yet authorized, together with a statement of the proposed method of financing them. In the absence or disability of the official or person regularly in charge of a department, the duties required by this section shall devolve upon the person next in charge of such department.