Budget21.com is a universal business planner for playing through the future of the company. A Web-based application enables an entrepreneur to prepare rolling budgets or a complete Business Plan. Budget21.com is a novel planning and budgeting tool - business simulator, which helps a manager to perceive better the functioning of his business. It is a software service which helps a decision-maker to foresee and play through "what if" situations. Budget21.com automatically generates solutions to expected economic performance and business situations. The quality of decisions will improve, as the expected situations can be played through in the computer. Thanks to business simulation, the opportunities and objectives of the company become clearer and it is possible to prevent crises and avoid management errors. Budget21.com shows what the cash flows, profitability and financial indicators of the company will be like in the future. It will be easy to determine additional financing needs, select timing for capital expenditures and plan the payment of dividends. The entrepreneur will also learn about the value of his or her company. On the basis of the inputs, Budget21.com will automatically prepare Budgets, Income Statements, Cash Flow forecasts and Balance Sheets, and will use the main financial indicators to characterise the value and profitability of the business in the course of five years, calculating each indicator by months. Budget21.com automatically compiles a full-lenght Business Plan consisting of the strategy and the financial projections. Besides entrepreneurs, Budget21.com is convenient also for bankers who can now use a common Web-based business model together with the loan applicant instead of handling business plans presented on paper. Budget21.com is a 100% Web-based application, the software is used as a service. No software is installed, it is sufficient to have an ordinary Web browser and Internet connection.