If you have added a secondment for an employee and they are currently in their seconded post, you will not be able to transfer them at this point.
To be able to transfer them to a new post you will first need to revert the secondment:
Search for the employee and go to their profile.
Click Employment and then Position.
Click Revert Secondment and add the end date of the secondment in the Return Date field.
Click Return Secondment.
Once this is done, the employee will be moved back to their original post. You can now follow the steps in our article on moving an employee to a different post in order to transfer them.