After the current expense budgets have been adopted and before the beginning of the fiscal year, the head of each department, office, and agency shall submit to the mayor in such form as the mayor shall prescribe a work program which shall show the requested allotments of the appropriations for such department, office, or agency for the entire fiscal year at least monthly or as the mayor may direct. Before the beginning of the fiscal year the mayor shall approve, with such amendments as he shall determine, the allotments for each such department, office, or agency, and shall file the same with the head of the division of finance who shall not authorize any expenditure to be made from any appropriation except on the basis of approved allotments. Such allotments shall be in conformity with the salaries established by ordinance, the provisions of any merit system applicable to such city, and the laws of the State of Alabama relating to obligatory expenditures for any purpose. The aggregate of such allotments shall not exceed the total appropriation available to each such department, office, or agency for the fiscal year. An approved allotment may be revised during the fiscal year in the same manner as the original allotment was made. If at any time during the fiscal year the mayor shall ascertain that the revenue cash receipts of the general fund or any public utility for the year plus any cash surplus available from the preceding year will be less than the total appropriations to be met from such receipts and said surplus, he shall reconsider allotments of the departments, offices, and agencies, and, subject to the laws of the State of Alabama and any municipal ordinances of the city relating to obligatory expenditures for any purpose, revise the allotments so as to forestall the incurring of a deficit; provided, however, that there shall be no reduction in salaries except by order of the council, or as authorized by law.