The law on car seats is actually very clear however there are a lot of people who don’t realise or simply don’t follow the government guidelines that are enforceable through law.
The most up to date guidelines on which seat is appropriate and safe for carrying your child can be found on the Gov.UK website.
The seats are categorised according to age and weight of the child and the website states that all children under the age of 12 or under the height of 135cm must use a booster seat.
There is some confusion around the exemption rules regarding a short unexpected journey, children over the age of 3 may travel without a child seat in these circumstances provided they wear an adult seatbelt. Children under the age of 3 cannot travel without a car seat in a standard vehicle.
And just when you thought you had it sussed there are also a separate set of rules for mini buses and taxis!
If in doubt look up the rules on the website but the basic rule of thumb is that children are much much safer in the appropriate seat on ANY journey and this should always be thought about prior to the journey commencing.