A budget is a financial plan for a defined period, often one year. A budget is an estimation of revenue and expenses over a specified future period of time and is usually compiled and re-evaluated on a periodic basis. A budget is a financial plan for a defined period, often one year. To put it simply, a budget plans future savings and spending as well as outlining projected income and expenses. A budget is generally a list of all planned expenses and revenues. What is Budgeting? What is a Budget? Budgeting is the process of creating a plan to spend your money.