Yes, you must, although you can enrol after the first occasion you need treatment. Australia has a reciprocal health agreement with the United Kingdom, Sweden, Finland, Norway, the Netherlands, Belgium, Slovenia, Malta, Italy and the Republic of Ireland, so it makes sense to enrol anyway as the Australian medical system is one of the best in the world, and it helps keep the premiums down! Obviously if you’re not a resident of one of these countries you can’t enrol, and your treatment will be paid by the insurers. There are Medicare offices in most large towns and cities in Australia, so just pop in with your passport and sort out your Medicare cover when you get there. If there’s no queue, it usually takes about half an hour to sort out.