For several years, many activities concerning ageing issues of dry storage casks for spent fuel have been going on. As an initial activity on the international level, a joint working group of the transport and waste safety committees of the IAEA, TRANSSC and WASSC, has worked on the subject. As a result, the group issued a TECDOC and the IAEA has introduced ageing management requirements in the 2018 revision of the Transport Regulations. Following the international activities and considering the foreseen long interim storage period, ENSI has identified the need for research and for administrative actions in the field of spent fuel dry storage. This resulted in several actions taken by the authority: issuing specific Swiss package design approvals for foreign dual purpose casks instead of validations (transport), introducing an obligation for any approved package design for dry storage to provide periodical ageing justifications, amending ENSI guidelines to introduce ageing management requirements for dry storage package designs, and developing a guide to provide a harmonized approach for ageing justifications. In accomplishing the identified actions a guide for ageing management of dual purpose casks (DPC) in dry storage has been published in December 2018 and will be presented by this paper. The guide intends to help users implementing an ageing management program and transferring the results into periodical safety justifications. Such justifications have to be provided periodically to the competent authority for review. The guide ensures a comprehensive and harmonised approach to ageing justifications issues by all relevant Swiss stakeholders. The guide provides advice for documentation, definition of relevant DPC components, analyses of ageing effects, definition of necessary measures, ageing of contents, implementing an ageing management program and evaluation of DPC ageing with respect to transportability and the foreseen storage periods. It identifies the corresponding responsibilities and takes into account the envisaged storage configuration. Based on the guide, Swiss stakeholders have already launched the implementation of the guide in a collaborative manner. This includes common procedures to address ageing issues for DPCs, update of management systems, and a roadmap for providing ageing justifications to the authority.