Adding a Miscellaneous Item you have to add the percentage of GST - this should either be is GST Free or Not.

The need to enter a % amount needs to be replaced with perhaps a check box, for either includes GST or doesn't, the software then needs to calculate the GST at the required %'age.  If this goes against other countries, can we have a template/tab that is set when you select Australia, where it has both Australian wording and defaults to 10% GST. 

Adding a Miscellaneous Item you have to add the percentage of GST - this should either be is GST Free or Not.  Under no circumstances should the User have the ability to edit the GST percentage or amount.  This is a ticket for disaster, if there is any way of getting something wrong a User will!!!