This confuses me too as an Aussie. Partly because we do our taxes July-november, but also because it’s just a simple form that’s mostly pre-filled here too. Businesses I believe do have a more complicated form to fill out, but as an individual person you just hop online, read through a few pages of pre-filled info (or what most people do: just spam next through it) and you’re done. They tell you how much they’ve recorded you paying in tax, you confirm it, then they tell you how much money you either need to pay or you get refunded (or nothing at all if you got your taxes spot on/don’t need to pay tax)