at what age child can sit in front seat

In Australia, the short answer is: not until they’re older, and even then the back seat is king. Children under 4 years must not sit in the front if the vehicle has two or more rows. From 4 to under 7, the front seat is allowed only if all rear seats are already occupied by children under 7, and they must be in the correct child restraint/booster with a lap‑sash belt. At 7 years and up they may sit in the front with a properly adjusted seatbelt, though safety boffins still prefer the rear until about 12 years (or roughly 145 cm). If your vehicle has only one row (e.g., a single‑cab ute), a correctly fitted restraint may be used in the front; never put a rear‑facing seat in front of an active airbag. Laws are nationally consistent, but check your state’s fine print—riveting reading, but cheaper than arguing with an insurer.