Add tax to subtotal

Add tax to subtotal

Hi, I would like to know how I would go about setting up an invoice template to be able to add tax to a subtotal.

The current tax settings seems to work out the percentage of tax from the subtotal (i.e. inclusive), but In Australia GST tax is added on top of the subtotal with a grand total displayed beneath.

I've tried both the Grand & Spreadsheet Plus templates without much success.

Is this possible at all?

Many thanks in advance.