NetBill is a business model set of protocols, and software implementation for commerce in information goods and other network-delivered services. It has very low transaction costs for micropayments (around 1 cent for a 10 cent item), protects the privacy of the transaction, and is highly scalable. Of special interest is the authors new certified delivery mechanism which delivers information goods if and only if the consumer has paid for them. The article discusses the design of the NetBill protocol and the authors' World Wide Web (WWW) prototype implementation. As the explosive growth of the Internet continues, more people rely on networks for timely information. However, since most information on the Internet today is free, intellectual property owners have little incentive to make valuable information accessible through the network. There are many potential providers who could sell information on the Internet and many potential consumers for that information. What is missing is an electronic commerce mechanism that links the merchants and the consumers. NetBill is a business model, set of protocols, and software implementation allowing consumers to pay owners and retailers of information. While NetBill will enable a market economy in information, it is still expected that there will be an active exchange of free information