Hi Amy,
Have you tried with 100% Withholding Tax (WHT) code? I assume you want to transfer the invoice to FullyPaid state and identify the invoice full amount as a tax obligation.
Hope this is not a backup withholding scenario. Because, you have mentioned that, you need to recognize 100% tax amount from the invoice. I am curious to know the real business scenario.
Now, I have a question for 1099 reporting.
How do you report 1099-Misc?
If you are using IFS tax ledger for 1099-Misc Reporting (I assume this is not a new news for you), you have to combine Zero WHT line for income recognition.
I agree with Eranda, out of the box, 100% WHT is the only real way to handle to remit to tax authority but recognise as liability originally to supplier.