If you submitted your tax return on time (and especially if you used e-Tax), chances are you've already gotten a refund by now. But if you're in the less fortunate category of owing the tax office money, those bills start falling due this week.
The ATO points out on its site that notices of assessment will begin being due from November 23. There's no sense in paying a tax bill before its due date, but there's no point in holding off beyond it, since you can get hit with interest charges. While the ATO has noted that its computer systems will be offline in much of January, you wouldn't want to rely on that when it comes to the taxman coming for his money.