A budget is a calculation plan, usually but not always financial, for a defined period, often one year or a month. A budget may include anticipated sales volumes and revenues, resource quantities including time, costs and expenses, environmental impacts such as greenhouse gas emissions, other impacts, assets, liabilities and cash flows. Companies, governments, families, and other organizations use budgets to express strategic plans of activities in measurable terms. Preparing a budget allows companies, authorities, private entities or families to establish priorities and evaluate the achievement of their objectives. To achieve these goals it may be necessary to incur a deficit (expenses exceed income) or, on the contrary, it may be possible to save, in which case the budget will present a surplus (income exceed expenses). In the field of commerce, a budget is also a financial document or report that details the cost that a service will have if performed. Whoever makes the budget must adhere to it and cannot change it if the client accepts the service. A budget expresses intended expenditures along with proposals for how to meet them with resources. A budget may express a surplus, providing resources for use at a future time, or a deficit in which expenditures exceed income or other resources. Source: Wikipedia (en)