Can large soft spot in head that is supposed to close around 18 mths age change its position with time . it seems to have moved towards back of head?

Soft Spot: Hello. If you are referring to an infants soft spot there are 2 of them called fontanels. One is located at the top of the head and the other at the back of the head. The one in the back should close between 2-4 months of age and the one on top should close no later than 2 years of age. If you notice that one or both are still open I would take your child to their pediatrician for evaluation.