A billing data interface provides billing data to customers in an accurate and efficient manner. Billing data is processed to preserve client billing information and to meet a customer's individual data requirements. The billing data may be presented in such a way that the customer may input the billing data directly into its client billing system. The billing data may be processed according to client billing specifications corresponding to a client billing system used by the customer. The processed data may preserve leading zeros, separate client code and matter code into two fields, etc. The resulting data file may be delivered to the customer for entry into the customer's client billing system.