Car seats and 5 year olds. If a child is regularly going in a car with a parent, three times a week for two 40 minute journeys each way, do they have to be in a car seat or a booster? To add he also has him for weeks in the holidays and drives longer journeys with no car seat. My ex is refusing to put my son in one. My son is 121.5cms and weighs 23kgs. I'm struggling to understand the Government guidance. I've offered a high back for him to use, and a booster to have, but he's completely refusing. The added issue is that my son also refuses to wear a selt belt and so his dad has disabled the automatic alarm. So he's just sitting in the backseat 70s style. Is there anything I can do about this? Am I being unreasonable? I'm so worried about my son. Is there somewhere where I can report to?