The Town at the annual meeting shall adopt a budget which shall include the proposed expenditure of each department for the coming fiscal year, and adoption of a budget at the annual meeting shall be deemed an appropriation to each department of the sum allotted in the budget for such department. A department's expenditures may not exceed the amount appropriated to it, except by consent of the selectmen and subject to the provisions of sections 1506 and 1507 of this charter. The amounts stated in the budget, and as approved by the Town, shall become appropriated to the several agencies, departments, and purposes therein named.