In its subsequent correspondence with the Committee, the Cabinet Office clarified that its Strategy’s £4.3 billion benefits figure had been calculated from a mixture of its dashboard and clusters’ full business cases. The Cabinet Office’s correspondence reported shared services’ change costs at £846 million in one section, and ‘around £1.6 billion’ in another section: as compared to a mid-range estimate of £4 billion had each department procured their systems individually. While giving no further details on 20 Treasury Minutes, Government Response to the Committee of Public Accounts on the Forty-eighth to the Fifty-fourth reports from Session 2022–23, CP 902, July 2023 21 C&AG’s Report, para 1.15 22 Qq 12, 71 23 Q 12 24 Q 11; C&AG’s Report, para 9, 1.16, 1.23 25 Q 12 26 Q 24 27 C&AG’s Report, key facts page 28 Qq 38, 39 11 the £1.6 billion figure, its £846 million cost calculation was based on HM Treasury’s commitment to Matrix, Synergy and Unity clusters in Spending Review 2025.29 These costs are therefore not calculated from the same baseline as the benefits the Cabinet Office has given. This is because they exclude the costs incurred by two other clusters (Defence and Overseas); by departments’ separate commitments, including funding for shortfalls left by HM Treasury’s spending review; and by HM Treasury’s approval of a further £300 million in reserve funding between 2021 and 2025.30 The fact that the Cabinet Office could not provide the high-level cost-benefit analysis we asked for at our hearing, appears to confirm lack of clarity in the Cabinet Office about this whole project.