Place Paid Before Sub-Total As A Row Item

I have notice that the Paid is placed on an invoice after taxes. This means that the client is paying interest on their payment. (See attached) Ideally a payment entered on an invoice would be a row and subtracted from the invoice items when calculating the sub-total. Taxes would than be applied to the subtotal.

[size=10]Last Update: 17.02.2016[/size]