The paper describes the methodology of variational interval budgeting in a system with hierarchical structure of expense items. The priorities of expense items can be specified at any level of hierarchy. To account for the actually existing information incompleteness, the methodology provides the ability to input data and receive the results as numeric segments. The ability to clarify the budget plan in the course of its implementation is also provided. The article presents main characteristics of the working online service “Cost Planning” and example of the farm budget planning