Ree787,
I have had a look at what your saying but it would be wrong.
The total amount is the total for the items as in qty * unit price. Then the subtotal is the total of the total amount. the vat column is the vat amount of the unit price * qty then the vat total for 20% is like the subtotal then the subtotals are added together to the grand total or over all totals. There is nothing wrong with the software. I was also taught to do it this way as well in school and also by very good friend who is a accountant.
If I seen the vat added to the total amount I would expect to see the subtotal to do the same.
Were are in as in country.
Also the next time you get an invoice for things you bough look to see if the done the way I have said above or the way you think it should be done