Everyone who is a resident in Australia for tax purposes is required to pay a Medicare Levy of 1.5% of their taxable income. The levy is deducted by your employer.
The catch is that if you are a Temporary Resident or Overseas Visitor (and not from a country that has a Reciprocal Health Care Agreement with Australia), then you cannot access the Medicare system. So you pay the levy but receive nothing for it.

There is a way of recovering your Medicare Levy from the Australian Taxation Office.

You must first apply to the Levy Exemption Certification Unit and ask for a letter from the Minister exempting you from payment of the Medicare Levy. Once you have this letter you must attach it to your tax return in order to receive a refund of the levy for the past financial year. It only works retrospectively, not for the year ahead. You must first pay the levy before you are allowed to be exempted from it and lodge a refund claim.

The form that you require, along with a full explanation, is available online at the Medicare Australia web page. (Medicare Levy Exemption form)

The application of this refund may vary according to your personal circumstances and so we advise you to always consult a tax professional about Australian Taxation Law.

If you have been issued with or are entitled to a Visitor's Medicare Card, also called a Reciprocal Medicare Card, then you are required to pay the 1.5% Medicare Levy with your tax. You will also be subject to the Medicare Levy Surcharge(MLS) of an extra 1% of your taxable income. Purchasing overseas visitors health cover does not necessarily exempt you from paying the MLS.