The main purpose of transfer pricing (TP) rules is to ensure that intra-group activities between related companies are carried out at arm's length, i.e. establishing a price that related companies would have agreed to if they were separate companies. TPs are not harmonized at international or EU level, thus countries are free to apply their own domestic TP rules. The Organization for Economic Cooperation and Development (OECD) published in 2010, the OECD Transfer Pricing Guidelines (OECD TPGS), which is an unofficial harmonization of TP guidelines internationally. As the OECD TPGS are general and worldwide recommendations for countries to follow, the wording of the OECD TPGS is, in parts, unclear and unspecific in terms of scope and application. The lack of a clear definition of ownership of IP has created room for interpretation and conflicts in international tax law between countries, which can cause double taxation or double non-taxation. The primary purpose of the thesis is to examine the provisions on the ownership of IP and how they are formulated in the TP from a national law and tax treaty law context, de lege lata, and with the secondary purpose of exploring these contexts, de lege ferenda, to provide a clearer understanding of IP ownership for TP purposes.