F110 Withholding Tax Calculation with Accumulation

Hi all,

I am trying to debug through F110 (SAPF110S) to find out the Withholding Tax calculation with WHT type with Monthly Accumulation (T059P-WT_ACCPT = 3) to find out how it transfers the calculated withholding tax amount to REGUP table with its rounding logic

Would any of you be able to advise me where/which subroutine/method or function modules is getting called to calculate the Withholding tax and passing the WHT tax amount to table REGUP so that I can place the breakpoint to start with or any further insight of SAP standard behavour of WHT calculation with month accumulation to REGUP table would be very much appreciated.

Thanks in advance

Taro