Chief financial officers (CFOs) tend to have a lot of different roles within a company. For small businesses, the role is even broader. However, most of the time, a company can't afford a CFO or doesn't need one for a good portion of its start-up cycle. That doesn't mean that the company can't benefit from the different roles that a CFO plays. They implement budgets, create forecasts, and are generally the forward thinkers steering the ship, financially. According to HBR, they are the "financial stewardship of the enterprise."
A good budget generally uses the past like a building block and integrates business goals into the numbers. But by spending too much time looking into the past, an owner will project what has already happened rather than prepare for what is going to be needed for the future. Although a budget should be completely realistic, it's OK to be a little off. Cash flow within the business can increase or decrease by certain accounts due to unforeseen circumstances throughout the year. These circumstances can be scary, but the budget can help you to be prepared for these unforeseen expenses. Entering the budget into QuickBooks month by month will also help you compare the budget to the financial forecast.