Hello. Unforunatelly, that's not easily supported by our component now.
You have to edit code manually.
1. First check if you can update to newest version (2.0.29). We will be releasing it in short time, so maybe it will be available when you are reading this.
2. open file administrator/components/com_vminvoice/helpers/invoicehtml.php
3. If using 2.0.29, on line 1616, if using 2.0.28 on line 1386 enter (its before $relevantCols line)
$subtotalTag = $subtotalTag2 = '{price_notax}'; //or any other tag which you use in last column
We are sorry it goes like that. We are thinking that we will improve whole template editing to be more flexible and simple in future.