Amortization posted with tax

Hellos Experts,

we use Zero-bond product for Bonds with amortization method that post
difference between face value and payment value

    users requirement is to calculate withholding tax posted with amortization
amount every month , percentage of amortization as 20%.

on Tcode TPM1 i tried it by derived flow but it didn't create any flow on
transaction FTR_Create.

any help please.