It depends on whether there is a change in the number of points used and when you make that change (for
DVC resorts). If you make the change 30 or more days in advance there is no penalty at all. If it is within 30 days and the number of points you use stays the same or goes up- there is no penalty. If the number of points you use goes down than the extra points automatically go into a holding account that expires at the end of the current use year. Holding account points can only be used for reservations made within 60 days of the stay.
If you change the dates on a nonDVC stay- such as the Disney collection in addition to the point rules above you have to pay a new $95 transation fee.