Koperasi Konsumen Republik Indonesia (KKPRI) Politeknik Negeri Seamarang is a cooperative that runs savings and loan businesses and shop businesses. The management of sales, purchase and inventory transactions is done manually and then inputted into the FoxPro program based on the type of transaction, cash purchases and credit purchases, inventories, and cash sales and credit sales. The system is less effective due to frequent data that does not appear and double input inventory, this hampers the transaction process in the cooperative so that employees delay data input and are manually disabled. The system development method used is the prototype method using the Unified Modeling Language (UML) modeling language. Development of the system using the PHP programming language and MySQL database. The results obtained from the information system built are applications that can generate information in the form of purchase reports, inventory reports, and cashier sales reports.