The books and accounts pertaining to the business authorized by this chapter shall be kept in a form to be prescribed by the board of commissioners, and the accounts shall be closed on the last day of July in each year, so that a balance sheet of that date can be taken therefrom and included in the report of such board, as provided in section 7-216, which report shall further contain an account of the financial condition of such business, the amount of indebtedness authorized or existing on account thereof and a list of the salaried officers employed therein and the amount of salary paid to each, and shall be accompanied with a statement, to be signed and sworn to by the clerk and superintendent mentioned in section 7-216, of the income and expenses of such business, in such detail as the board of commissioners requires. The selectmen of a town, the mayor of a city or the warden and burgesses of a borough may direct any additional returns to be made by the board of commissioners or by the superintendent and clerk at such times and in such detail as they order.