The present invention relates to flexible billing systems that can be used within the transportation industry to facilitate credit card billing adjustments to credit cards that were previously used by customers to pay for one or more shipping charges. In particular, the present invention provides a system or tool that enables a user to easily access a detailed billing history of credit card transactions in order to apply full or partial credit card billing adjustments that specifically correspond to individual transactions included in the history of charges associated with a particular item or shipment.