A computerized method and system for combined billing for at least one customer on a plurality of customer accounts includes computer applications which automatically assemble and aggregate account charges, such as usage charges, fees, finance charges, discounts, rebates and rewards, for the customer on the plurality of accounts. The system also automatically formats a combined bill for the customer from the aggregated account charges and renders the combined bill to the customer. The account charges are automatically calculated by a computer application from account data for the customer's accounts, which is transmitted to the computer application from one or more storage devices, for example from vendors of energy, such as electricity and gas service, retail, such as credit cards, and communications, such as telephone and Internet service.