Let's take a look at a few popular retailers' returns policies, which are in addition to your usual legal rights. (Click on links for full details.)
Kmart and Target have the same change of mind policy, with some products excluded. You must return the product within 60 days of purchase (or 365 days for paid OnePass Members), with "adequate proof of purchase". Other conditions include that it's unworn, unused and "in resaleable condition".
Big W has a 90 day change of mind policy, with some exclusions. Like Kmart, you'll need proof of purchase, as well as the item being unworn, unused and in saleable condition.
Myer offers 30 day in-store refunds or exchange on most items. Purchases from November and December can be refunded or exchanged until January 31. You'll need proof of purchase. And there are exclusions, such as clearance items.
Amazon's changes of mind policy covers items sold by Amazon AU – not third parties sellers. Returns must be sent back in new, unused condition. Most items bought in November and December can be returned for change of mind until January 31.