A successful UAT is one where the business can show that they are comfortable with the application features, and thorough testing has been done with good involvement of the business users across areas. The key deliverable of UAT is the business sign off on the (UAT) and test results. There may be cases where items do fail, but the team agrees to a conditional sign off. Track any bugs that are critical for going live as a part of this conditional sign off. Most importantly, all areas should have been tested by now. There is a difference between knowing the open issues and being unable to test specific areas due to open issues.