In the present study we examine the crystallographic structure of the , ’’ and phases present in nickel base 718 alloy. The chemical ordering of Nb atoms and possible planar faults that may be observed in ’’ precipitates are detailed. High resolution transmission electron microscopy (HRTEM) observations of various faults are reported. The decomposition of a matrix dislocation to form a locked V shaped configuration is shown. The observation along  type direction allows to identify the type of defect, which is observed as a pure geometric stacking fault.