Children often lie to protect themselves. If parents aren't pretty sure that their child has stolen something, they probably should not apply consequences. Instead, they should let their child know that they are skeptical, and express hope that their child will be honest with them. Parents should make sure that their children have some sort of regular income. If children have money of their own to spend as they wish, they will be more likely to buy what they want instead of stealing it.
Children can earn money by doing chores around the house, etc.
Don't shame children for stealing. Parents should try not to make their children feel guilty for stealing. They should also try not to call their children names, for example a thief or a liar. Such tactics can be very damaging to children's self-esteem. Instead, parents should let their children know that they are disappointed in their children's behavior, but this does not mean that they are bad people.