If the tax reference is the same on both payrolls, the employee's payroll can be changed by following the steps below:
Search for the employee and go to their profile.
Click Payroll and then Pay.
Click Edit in the Pay Details area.
Select the payroll from the Payroll dropdown list and click on Save.
However, if the Payroll Tax Code is different, you will get the pop-up message 'Not allowed to transfer to a payroll with a different tax reference' when making the changes above.
In this instance you will need to terminate this employment and create a new one for the employee that has the correct payroll selected.