On or before the first day of June in each year the city manager shall submit to the council a tax budget for the ensuing fiscal year. For that purpose, at such date as he shall determine, he shall obtain from the head of each department or agency of the city, plans for the work to be undertaken by such agency during the next fiscal year, together with estimates of the cost of performing such work. The department of finance shall supply him with estimates of probable revenue. From these data the city manager may revise the estimates and prepare his recommendations for the tax budget for the ensuing fiscal year.