Hi,
SAP has a provision to run forced retro to recalculate from back-date and get the revised wage types.
However, once the Ptax is remitted to third party (Govt.), it is difficult to get it back. For income tax, you have the refund procedure.
But for professional tax, you have to check with the concerned govt. department for the same.
Better, you run the forced retro payroll in your test system for checking the values.
Only after confirming, you run in live system.
regards,
Bala.