Typically you will need to lodge a DA amendment form, depending on how substantial the changes are. If the changes are major, where they change dwelling footprint, orientation, or create new non DTC issues or things like overshadowing issues for new neighbours, you will need to amend the DA. Small changes like some roof form changes that don’t change overall building height, and opening reductions, can be adjusted at local government discretion and be considered minor amendments and be dealt with at BP stage.