How Do I Add The Tax To The Marketplace Fee Without It Being Added To The Balance?

I have activated Direct Customer-to-Vendor Payments Addon
I need to tax 18% of a vendors marketplace fee
I tried adding 18% for the product "Marketplace Fee"
Balance: -100
When the vendor tried to refill a balance of 100
He is charged 118(tax added) as expected and Invoice comes out as expected
In the refill balance section, it is showing as Balance: +18 now
How do I add the tax to the marketplace fee without the tax being added to the Balance?