The illicit trade with cultural property is a worldwide problem. Many of the cultural properties that are traded have been plundered and exported from countries and end up on western markets, often at auction houses and auction platforms online.  This study aims to understand the responsibility Swedish auction houses and online platforms have regarding the illicit trade with cultural properties. This is achieved by answering the following questions: what responsibility does the auction houses and online platforms have? Do they take this responsibility? Do auction houses and online platforms have policy documents regarding cultural objects? What do these policy documents in that case look like and can they be improved? Is there a difference between the policy documents of physical auction houses and auction platforms online?  To answer these questions this study focuses on three main areas of sources: document analysis of legal and policy documents, previous research and articles published in the field, as well as five qualitative and semi-struc- tured interviews. These sources are discussed throughout the analysis which have been divided thematically. An overview of the trade in Sweden culminates in a discussion about due diligence and provenance. Further, a discus- sion of the auction houses responsibilities and policy documents is followed by chapters discussing the same ques- tions in regard to the online platforms.  Conclusions which have been drawn from the empirical analysis are that the auction businesses take respon- sibility to a certain degree but that policy documents and the transparency in public discourses can be improved. Furthermore, they should be clear that they use due diligence and actually make sure that they do it in their daily activities.  This is a two-year master’s thesis in Museum and Cultural Heritage Studies.