This is the million-dollar question. There is no absolute answer to this question. The best time to consider toilet training is between the ages of 18 months to 3 years. If someone tells you to start potty training at a certain age, then they are missing the point or making a general assumption that you and your child are ready. The best time to toilet train is when you and your child are ready to toilet train. There is no magic age or cutoff.
Choose a time and situation that is most comfortable to you and your child. Be prepared for a simple process, but do not be surprised if potty training does not come easy. In other words, every child and every family situation is different. Some kids are easy to train and others are very hard to potty train. Pick your time to train, do not let others decide for you. Be prepared for the best and the worst of potty training experiences.