The CMORG Collective Action Firm Shutdown/Sector Restart Playbook enables the sector to shut down and restart on a coordinated basis in the event of a major operational disruption. The playbook was developed in support of SIMEX24, which explored the impact of a national power outage (NPO) on the UK financial sector. The playbook could be relevant in other extreme scenarios, for instance a major cyber-attack. Developed under CMORG governance and aligned with the UK Financial Authorities’ strategic planning, it outlines the procedures for alert and notification, firm/FMI level response during and immediately following an outage, resumption of services, sector restart, communications, and remediation and restoration.