This chapter describes how a specification conveys the needs of the customer while providing a common basis for comparison of supplier proposals. To this end, we discuss the main items covered by the specification, including the requirements for the automation solution (e.g. parts to be processed and production rates) and the customer requirements for the execution of the project (e.g. project management expectations and project timing). We also address the key issue of buy-off criteria, together with the testing stages that should be performed within a project.