777newbie if you are flying an Australian Registered aircraft then Civil Aviation Order 20.16.3 applies:
Seats
3.1 Each crew member and each passenger shall occupy a seat of an approved type:
(a) during take-off and landing; and
(b) during an instrument approach; and
(c) when the aircraft is flying at a height less than 1000 feet above the
terrain; and
(d) in turbulent conditions:.......
Seat belts and safety harnesses
4.1 Except as provided in subsections 14 and 15 safety harnesses, or seat belts where safety harnesses are not fitted, shall be worn by all persons at the times listed in paragraph 3.1. Seat belts and safety harnesses shall be adjusted to fit the wearer without slack.