Default tax code as part of the contact details.

Shouldn't each customer or supplier have a default tax code as part of the contact details, or at least an option to specify that a customer is exempt or that supplier is unregistered, so that any invoice or bill would default to the usual GST code for that customer or supplier if the item also has a GST code. Non GST registered suppliers and exempt/export customers would therefore default to "none" or zero even if a particular item has a default GST code already, so for example my unregistered subcontractor doesn't get paid GST by mistake.