Australian Institute of Health and Welfare. (2011). Substance use among Aboriginal and Torres Strait Islander people [cat. No. IHW 40]. Retrieved from
Where a report has a document number include in square brackets after title, e.g. [doc number 12345].
Aboriginal and Torres Strait Islander people were more likely to visit a treatment centre than their non-indigenous counterparts (Australian Institute of Health and Welfare [AIHW], 2011) resulting in ...
Assistance was commonly provided for alcohol, tobacco,and marijuana (AIHW, 2011) which indicates ...
Use full name for first citation with acronym in square brackets 
Note: If the full name is part of the sentence structure use round brackets () e.g. The Australian Institute of Health and Welfare (AIHW) suggests that...
When using online resources with no page numbers use paragraph descriptors e.g. (conclusion, para.1).