A dynamic claims adjudication system is provided that implements a dynamic claims adjudication process to provide flexible determination of the adjudication rule set to be used to adjudicate a claim for a particular prescription drug regardless of the mandates of the formulary and the rigidity of the tier into which the drug is placed on the formulary. The claims adjudication system and corresponding methods dynamically determine the adjudication rule set to be used to adjudicate a claim based on an analysis of criteria and identification of a tier changing criteria. Accordingly, the rigidity of conventional formulary based claims adjudication is eliminated in favor of dynamic and flexible real time claims adjudication.