when can kids sit in booster seat

Kids can sit in a booster seat from around 4 years old, once they’ve outgrown their forward-facing child seat with an inbuilt harness. By law in Australia, children aged 4 to 7 must use either a forward-facing seat with harness or a booster with a correctly adjusted lap-sash belt. After 7, keep them in a booster until the adult seatbelt actually fits: belt across the mid-shoulder, lap belt low over the hips, back against the seat, knees bent at the edge, and they can stay upright the whole trip.

Translation: it’s about size and fit, not birthday cakes. Use an approved booster, anchor it properly, and don’t wedge it with towels like it’s a wobbly cafe table. When in doubt, check your state’s road authority guidance and err on the side of keeping them boosted longer.