In SPRO follow this path.
Extended Witholdong tax
Withholding tax certificates for vendors
maintain no.groups and script forms.
For cheques and Payment Advisory.
Go to FBZP
click on printmethods in company code
click on position
give Company code and payment method
then in the next screen double click on the payment method
This way you will get to see the forms assigned to it.
For Forms for Correspondence.
define form names for correspondence print.
This way you can find the corresponding scripts.Check TTXFP table too.