If you are the parent, legal guardian or a family member related to the child who has been given permission by the p/g, it is legal to hit a child as long as it is not hard enough to physically harm them with bruises etc. e.g. an aunt could give a light smack on the buttocks for bad behaviour as long as the child is not in pain and does not suffer. A mum cannot hit the child and leave a bruise. This applies in england as far as i know.