I have noticed that the Report Sales invoice by Customer includes VAT whereas the Report Sales invoice by Item doesn’t. Any reason for this? Could the one by customer be modified so it also shows figures without VAT? Or maybe can a function be added so that one can choose whether to have VAT or not in both report?
In the first case, the report totals invoices by calling on the customer subsidiary ledgers. Those entries include VAT, not as separate components, but as part of a single number. In the second case, the report totals amounts posted to inventory item subsidiary ledgers, which do not include VAT. (VAT is posted to a separate account.) So it isn’t a matter of toggling display on or off for something that is there as a separate variable.
My point is that the place the first report draws from doesn’t have separate VAT numbers. And the place the second report draws from doesn’t have VAT at all. As a result, what you ask for would be entirely different reports, not modifications of existing ones.
Meanwhile, have you tried getting what you need with custom reports?