Previous tax period adjustments - Flexibility

Scenario: EP payrolls are open for the September 2024 run (Month 06).
Two employees were meant to go from from one EP payroll to another EP payroll wef 19/08/2024 but this was missed and we need to backdate the adjustments as they were overpaid on the old employer.

Rather than deleting the September 2024 runs and rolling back the entire payroll(s), the adjustments can be performed in the current September 2024 run(s) as long as we have the following functionality. We can already change the pay date for the adjusting payslip back to the last month but need to ensure the associated RTI entries which are produced separately are flagged as a correction to previous submission (H) automatically.

Ability needed to force the tax period for these adjusting payslips to Month 05 the previous period.

Ability to override the tax period for P45 production (Month 05 required in this case)
Adjustments to be merged into Month 05 P11 entries (and not record them as Month 06 adjustments).

It is a feat that not many good payroll systems can do (I could do this on Payrite).