What is a budget and why do we do it? A budget is an essential planning tool for estimating your business or personal future income and expenses. A budget can be used to set goals and priorities and ultimately determine what you can and can’t do from a financial position. What it doesn’t do, however, is produce itself—however much we wish it did! But how do you budget for a budget? Or, in other words, how do you ultimately decide what to prioritize when making a budget?