When you change the Organizational Assignment infotype (IT0001) after a productive payroll run, the system checks whether the change affects the payroll results of the previous periods.
If the change affects the payroll results, the system triggers a payroll retroactive calculation for the employee in the next payroll run. This means that the system recalculates the payroll results from the earliest retroactive accounting date to the current payroll period, and adjusts the differences accordingly.
If the change does not affect the payroll results, the system does not trigger a payroll retroactive calculation, and the payroll processes normally. References = SAP Help Portal: Payroll Retroactive Accounting
[SAP Help Portal: Organizational Assignment (0001)]