Applying discount after GST?

[CootaParkBlue-E]

Hello,

Our business sends regular invoices from one particular company. They send us a report and then we create the invoice based on it. Their report has the invoice total, then adds GST, then subtracts levies from this total. 

Is there any way to do this in square invoicing? So far i've been using a dollar discount in lieu of the levies and just adjusting it so that the invoice total is the same, but it's not reflecting the actual levy amounts and they are starting to get frustrated. 

Thanks!