A software system and method for managing special or complex billing for large utility customers is disclosed. Utilities that bill customers for usage of a commodity or service (e.g., electricity, natural gas, water, oil or gasoline, the phone, cable, mobile communications, or another metered service) may use the software system and method to produce invoices or billing statements for their customers. Special billing requirements for each utility customer may be based on special billing products (228, 232, 200, 202, 204, 206, 208, 210, 212) offered by the utility. Data regarding the special billing products may be entered into a product allocation table (234) along with customer (200) and usage data (228, 232, 202, 204, 208, 210, 212). The software system and method automatically calculates billing determinants (236) using the product allocation table data and applies appropriate rates and charges to produce an invoice (238) or billing statement.