For the UAT phase of an implementation project, a detailed task and communications plan is especially important. It precedes the launch phase and is dependent on a number of stakeholders providing feedback by a specific date.
Ensure all testers know your UAT dates, build all tasks into a plan, and include the required effort. They need to know what is expected of them. Give adequate time for testing, but not too long (or you will lose momentum). Typically 2-3 weeks is the sweet spot for a full ERP implementation project.
Remember, in a software implementation, you are testing the agreed processes and workflows as mapped to your business and configured in the system. You are not testing the functionality of the software.
A well-planned and executed UAT phase is usually indicative of successful software implementation. There are several factors that will ensure a successful UAT phase from the perspective of both the client and the implementation partner.