Both the demerger and subsequent sale are CGT events. You should have script for script rollover relief for the demerger (i.e. no gain to report on this), but will have to declare the Coles sale. You will pay tax if your proceeds are greater than your Coles shares cost base. The cost base will be a proportion of your WES cost base. If they proceeds are lower you will have a capital loss to offset other capital gains or carry forward.
Check your return to see if it addresses this. It will be in the capital gains section, or if you accountant has printed the worksheets, will have a full worksheet for this. Otherwise just contact them to confirm.
