Corruption is considered to be one of the most important problems in today’s world. Corruption occurs in international commercial arbitration, too, despite the existence of various international conventions and national laws prohibiting corruptive behaviour. In this paper we focus on proving corruptive behaviour in context of international arbitration. We analyse the concepts of burden of proof and standard of proof and the difficulties associated with the two concepts. Thus, we evaluate whether reversal of the burden of proof should be applied in relation to proving corruptive behavior and we estimate the impact of lowering and heightening the standard of proof. We suggest a solution to overcome the issues associated with both concepts.