This paper examines the issues surrounding the charging for the use of electronic documents. While traditional systems charge for the release of the document, we have adopted the approach of distributing intelligent documents (agents) that can initiate the billing procedure when the user wishes to view the document. We first present the requirements that should be met by a system responsible for the sale of electronic documents, followed by a presentation of our approach for meeting these requirements. Finally, we discuss how this mechanism will be used in the construction of the HyperNews system for the sale of electronic newspapers.