First non-destructive measurements of XPS core level binding energies for group IVb-VIb transition metal nitrides are presented. All films are grown under the same conditions and analyzed in the same instrument, providing a useful reference for future XPS studies. Extracted core level BE values are more reliable than those obtained from sputter-cleaned N-deficient surfaces. Comparison to Ar+-etched surfaces reveals that even mild etching conditions result in the formation of a nitrogen-deficient surface layer. The N/metal concentration ratios from capped samples are found to be 25-90% higher than those from the corresponding ion-etched surfaces.