As previously predicted, free S$20 (~A$19.70) voucher offer has been extended to 30 September 2018 (and possibly thereafter - watch this space).
Too many conditions to list again - can all be found here in this excellent post from Mister Miser https://www.ozbargain.com.au/node/301477
Happy shopping….. yippee!
EDIT: It appears there have been some changes to the T&Cs listed in the Mister Miser link. Suggest you refer to current T&Cs.