The Australian Taxation Office
The ATO is the government entity entity responsible for collecting taxes within Australia. It polices the tax legislation and the requirements that the population has as a result of it.
The taxation administration act 1953 states that there shall be a commissioner of taxation who is responsible for implementing the tax laws. He is the head of the ATO.
Taxation policy in Australia is generally to let taxpayers submit their own returns every year and operate on the belief that they are correct. This removes the need for processing the return and the weight that processing every persons return would have on an organisation. If there are indications that a return is incorrect the ATO can review/audit a return and make corrections.