The first of these follows the procedures observed when preparing the scheme itself involving, among other things, approval by the Governor and tabling in both houses of Parliament where motions to disallow the amendment may be passed. (s. 33). This is referred to as a  'substantial' or 'major' amendment.

The other procedure involves matters which in the opinion of the WAPC do not involve a substantial alteration to the scheme and are referred to as 'non-substantial' or 'minor' amendments (s. 33A).