Horizontal monitoring has been established as a tool to prevent aggressive tax structures. It is based on the change of the traditional relationship between tax administration and taxpayers. The program concentrates on corporate taxpayers, mostly large business, with exception of the Netherlands where includes large business, but also small and medium sector. Tax relations are based on the cooperation, mutual trust and transparency between tax administration and taxpayers. After accepted into program, taxpayers sign agreements with the tax administration (tax intermediaries sign the agreement on behalf of the group of their clients - small and medium enterprises). The agreements define tax rights and duties of both parties in line with the law. The paper gives an analysis of the horizontal monitoring as a concept and its features in the Netherlands that make its program unique comparing with similar programs in other countries.