Go to Reports in the Tasking Zone, then further select Payslip, Payroll and PAYE - View Print. Then select P45 and the tax year and then the employees as appropriate for whom you would like to print P45. Further follow the on screen instructions to print the P45 forms onto the HMRC's pre-printed stationery.
Road Map - Print P45 Report
Reports -> Payslip, Payroll & PAYE - View / Print -> P45 Link -> Continue button -> View / Print Link
( 'Reports' is the button positioned in the tasking zone menu at the top. It is the second button from the right)