So if the House introduced a 'fixed' VAT tomorrow, say $1, not proportional to the price of the product, would that not break most software used to compute VATs

So if the House introduced a 'fixed' VAT tomorrow, say $1, not proportional to the price of the product, would that not break most software used to compute VATs? We have to make assumptions. Good software doesn't account for every future possiblity, but it is easy to change when the requirements change.