Hi MJ
Are you aware of s98(1) ITAA 1936?
http://www.austlii.edu.au/au/legis/cth/consol_act/itaa1936240/s98.html
INCOME TAX ASSESSMENT ACT 1936 - SECT 98
Liability of trustee
(1) Where a beneficiary of a trust estate who is under a legal disability is presently entitled...