How can we change logic of Tax Amount in "Tax Control Amount" field?

Summary:

On Supplier Portal when creating an invoice, supplier enters Tax amount in “Tax Control Amount” field. Currently there is a validation on this field that we cannot enter Tax Control Amount greater than the invoice amount. For e.g. if the invoice amount is $100, I cannot enter Tax Control amount more than $100. However, our business wants to investigate if we can change the percentage of what can be entered in here. For e.g. can we change the logic of the field to not allow the user to enter more than 20% of the invoice total. If the invoice amount