This Guide considers current challenges in building and maintaining perceived and effective impartiality amongst NCPs and identifies good practices and tools in this regard. In particular, it addresses the notion of impartiality mean and how is it challenged by perceptions of bias and conflict of interest, and discusses how institutional arrangements can be used to build and maintain impartiality in the NCP system. It also discusses how NCPs can build and maintain impartiality at the individual level, by reference to measures and tools that NCPs are currently using.