According to the American Association of Orthodontists (AAO), you should bring your child to a screening no later than 7 years old.
By the time they reach this age, your dentist or orthodontist will be able to best predict if your child will have any serious problems down the line. At 7 years old, their first molars erupt which establishes the back bite. Also, their teeth and jaws are developed enough that your dentist or orthodontist will be able to tell if your child might have any serious problems in the future. For example, if your child has erupting incisors, it may mean they will have possible crowding, an over bite, or an open bite.
That’s not to say that your child will need treatment right then and there. It’s more for you and your dentist to monitor your child’s development. Both of you can then plan on the best treatment options and help prevent serious problems from happening.