A National Survey for Australia on this subject has not yet been conducted as far as my research has shown.

http://www.ratbags.com/rsoles/comment/hillsong.htm

This page speculates that one Church, Hillsong Church had an annual untaxed revenue of $30 million in 2004.

http://tinyurl.com/98wvafw - BRW Report showing figures of how much is left untaxed. The catholic church got $16B in 2005.

http://tinyurl.com/c4tsyp6 - The Catholic church has been caught rorting the job payments scheme.

http://tinyurl.com/cu8wrzz - Recently an Islamic school was ordered to repay $9m that they misused.