The P45 is available on the Payroll by Month screen, to navigate to this screen select Payroll from the main left hand menu (circled below in red).
Then press the “Employer Payroll Setup” button (circled in red below).
Then press the “Set Employee, Salary, Bonus & Benefits” button (circled in red below).
Select the employee from the drop down box and press the “Monthly Payroll” button.
Press the “Download P45” button (outlined in red below). The P45 will appear in a new browser window.