The NEA Committee on Decommissioning of Nuclear Installations and Legacy Management (CDLM) and the Technical Advisory Group (TAG) of the International Co-operative Programme for the Exchange of Scientific and Technical Information Concerning Nuclear Installation Decommissioning Projects (CPD) addressed the topic of “Feedback Mechanisms for Lessons Learnt” in the topical sessions of their 2021 meetings. This brochure summarises the key findings.