Anytime! Don't under estimate what your child is capable of! I was a bit hesitant at first of the unknown, and everyones response to me starting potty training early, but stay strong, consistent, and Positive and your child will learn. My son Zachary and I waved bye bye to nappies at 15 months, by 16 months he had full bladder control with wees on the potty and by 18 months we got poos on the potty too! I waited to transfer him to the toilet after the birth of my second child, so at 21 months he has already nearly mastered it. I am going to start earlier for my second :)