Article 37 of the General Data Protection Regulation (GDPR) obliges data controllers and processors to designate a data protection officer (DPO). As part of this obligation, data controllers and processors are also required to publish the contact details of the DPO and to communicate the DPO's contact details to relevant supervisory authorities. In part one of this Insight series, OneTrust DataGuidance focuses on the requirement to communicate DPO contact details to the relevant supervisory authorities, providing an overview of the rules and guidelines for DPO contact registration across Hungary, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, and the UK.