In Australia transition altitude is 10000ft. For all operations at or below transition altitude use local or area QNH. For cruise in the standard pressure region use 1013.2 hPa. (29.92) There is also a transition layer where:
FL125 navbl when area QNH is below 963 hPa
FL120 navbl when area QNH is below 980 hPa
FL115 navbl when area QNH is below 997 hPa
FL110 navbl when area QNH is below 1013 hPa
Cruising within the transition layer is not permitted.