Section 56. The fiscal year of all towns of the commonwealth shall begin with July first and end with the following June thirtieth, and the returns made to the director under section forty-three shall show the financial condition of the town at the close of business on June thirtieth; provided, however, that the treasurer shall, until July fifteenth, enter in his books all items for the payment of bills incurred and salaries and wages earned during the previous fiscal year, excepting payment of school teachers’ salaries which have been deferred under the provisions of section forty of chapter seventy-one, and expenditures thereof shall be deemed to be as of June thirtieth preceding.