A unified model for nitrogen oxide abatement is suggested. The model observes that nitrates are the most common surface species on oxide supported catalysts under literally all conditions below the light-off temperature. The three routes for nitrogen oxide reduction; (i) direct decomposition, (ii) selective catalytic reduction (SCR) with ammonia and (iii) hydrocarbon driven NOx reduction, merely become different ways to destabilize surface coordinated nitrates. Nitrates are decomposed by thermal excitations in direct NO decomposition and by reactions between NO3 and NH4+ in ammonia SCR. Reactions between NO3 and hydrocarbon derived ligands rationalize the importance of partial oxidation products for the third route. The model stresses the significance of Cu2+-O-TM+ dimers for dual ion exchanged catalysts and lattice flexibility for direct decomposition over aluminum rich ZSM5 [TM = Transition Metal].