Withholding Tax Payment Remittance

We are looking to enable automatic withholding tax for some suppliers and have a question about how the payments should work for these scenarios.  I have setup the withholding tax functionality and have tested that the automatic invoice to the tax authority is created and the amount is withheld correctly on the invoice.  From a payment processing perspective, now that I have the amount automatically withheld from my vendor's invoice, how do we indicate on the payment remittance or anywhere that there was $xxx.xx amount withheld from the payment?  How should this process typically work?

Thanks,

John