If that's the case PHX, what happens when July 1 rolls around,...

If that's the case PHX, what happens when July 1 rolls around, 80% has not been obtained so a CGT event has occured for anyone that accepted the MIN deal.
For example let's use Joe Citizen.
Joe does his tax and it is processed. He is an individual that likes getting his tax done early.
He then pays his tax bill, then say 80% is obtained in Sept. Will the ATO provide a reimbursement or refund for over paying tax when he didn't need to?