Amending employment status and Start/Continuous employment dates

Amending employment status and Start/Continuous employment dates - currently the system does not allow a change to start or continuous employment dates when you change an employees contractual basis i.e from Casual to Permanent.

If there are any entries in their planner before the date that is their new start/continuous employment dates the system will not allow a change and I was advised to end that profile - essentially process that staff member as a leaver - and then rehire them even if they are NOT leaving and will retain their Casual role.

This then creates a report that shows that staff ember as a leaver. When sending the report to our external payroll company we do not wish to show this staff member as a leaver as it will trigger their P45 etc.

Why can the system not allow a change to start/continuous employment dates even when there is entries in the planner prior to that new date?

We are trying to move away from manual amendments of our payroll report and move to utilising the Query reporting form PeopleHR to send to our payroll bureau so would love a resolution to this if possible?