Hi M Layton, Thank you for your enquiry. The Britax Parkway Booster can only be installed using Isofix. Lap belts cannot be used when installing Booster seats. This seat is recommended for a child weighing 18kg – 54kg (approx 4-12yrs). As an alternative to installing Isofix into your vehicle, which is an expensive option, If you follow the link https://www.babyonthemove.co.nz/car-seat/shop-by-type/child-restraints-and-harnesses/Protecta-Plus this will take you to the Safe ‘n’Sound Protecta Plus Harness available to purchase online. This can enable your child to safely sit in a booster in a vehicle without Isofix. We would recommend visiting your nearest Baby On The Move store where one of our expert Car Restraint Technicians can help you with installation for this and help find the right car seat for you, your child and your vehicle. If you follow the link this will take you to our online store finder where you can find contact details for your nearest store. We hope this has helped with your query.