At the request of the management of CERN, four extensive Cost and Schedule Reviews (CSR) of both the LIU and the HL-LHC projects were carried out in March 2015, October 2016, March 2018, and November 2019. An international panel of experts, headed by the CERN Machine Advisory Committee chairman and composed by the CMAC members and several other personalities of the worldwide accelerator community, have scrutinized the two projects and their main work-packages, following a set of charge questions by the Director for Accelerators and Technology at CERN. After each CSR, the experts panel has issued a set of recommendations to the two projects and CERN management.

While the LIU project was successfully deployed during the Long Shutdown 2, the HL-LHC project is moving from the prototyping phase to the series production phase for all major work-packages. Since the last CSR, the COVID-19 pandemic has swept the world, also affecting the HL-LHC project. The next Cost and Schedule review will take place at CERN, between the 8^th and the 10^th of November 2021, exactly two years after the previous one, focusing with the completion of the LIU project now exclusively on the HL-LHC. Mandate and charge questions to the reviewers are presently being finalized by the ATS Director.

Work in preparation of the review has already started. Minor revisions of the Budget plan of several work-packages are regularly implemented through minor re-baselining exercises, after approval of changes by the project leader at regular project steering meetings. The strategy for securing spare equipment has been defined in detail for all work-packages. Procedures to link the schedules of interlinked work-packages are being implemented. CERN manpower and industrial labor resources will be reprofiled during the summer months, to deploy and support plans to recover from the COVID-19 induced shifts. In the coming weeks, the project office will receive the charge questions, which will be filed across the project in specific questions to work-package leaders. The collaborating institutes will also contribute, presenting progress and plans.

The review itself will be a blend of plenary and parallel sessions. While all themes crossing the whole project will be presented in one day exclusively devoted to plenary talks, the parallel sessions will give the occasion to work out all major technical and infrastructure work-packages. Infrastructures and testing facilities exploited by several work-packages will not be neglected, while a specific attention will be devoted to the IT String Test, as one of the major upcoming milestones and testbench for the integration and integrated operation of several of the most critical pieces of equipment.