Withholding for different tax authorities

Hello,

I am trying to test workaround #3 suggested in document 1413879.1, section “Accounts Payable Withholding Tax (R04580) Questions”, question #2 "Is it possible to set up a supplier to have two different withholding tax rates for different tax authorities?".  However, R04580 ends in error because I do not have a tax authority on the supplier master record.  Which tax authority should I enter on the supplier master record if there are several tax authorities involved?