can a 5 year old sit in the front seat

Short answer: in Australia, a five-year-old belongs in the back seat in an approved forward-facing child restraint or booster.

They can only sit in the front if all rear seats are already occupied by children under seven—and even then they must use an appropriate booster/child seat and the seat should be slid back as far as practical.

Never put a rear-facing restraint in front of an active airbag, and avoid the front altogether if you can because airbags and small humans aren’t a happy combo.

Best practice is to keep kids in the back until at least seven (and preferably longer) with the right restraint for their size.

Do the right thing and you’ll dodge fines and, more importantly, keep the small co-driver intact.