You can export payrun data from the drop-down on the payrun page.
There are two different formats available.
This gives you a CSV with similar rows and columns to what is displayed on the screen.
This gives you a CSV with potentially multiple lines per employee.
There is a line for each editable amount on the payslip (i.e., not PAYE, NI, etc.).
You can use this format to import payments to a payun.