A new, “radically" shorter Green Book will be published “at the start of 2026” according to the results of a review into the Treasury’s guide on how to appraise policies, projects, and programmes.
The review, which was launched in January 2025 and published today alongside the Spending Review, set out to consider whether the Green Book was being used in a way that ensured fair, objective and transparent appraisals of projects outside London and the south-east of England.
Delivering her statement in the House of Commons today, chancellor Rachel Reeves said she had heard concerns from fellow MPs and the Liverpool Metro Mayor Steve Rotherham that “in the past, governments have under invested in towns and cities outside of London and the South East”.
As a result of the actions set out in the review, she said: “Our new Green Book will support place-based business cases and make sure no region has Treasury guidance wielded against them."
A new taskforce – bringing together the Treasury, the communities and transport departments as well as participants from local and regional government – will develop an approach to building place-based business cases and oversee the implementation of this approach across the public sector.
The taskforce will be led by the Treasury’s second permanent secretary responsible for regional growth , along with the director general for local government, growth and communities in the Ministry of Housing, Communities and Local Government, and the director general for public transport and local group in the Department for Transport.
In a further signal of the need to involve local and regional government in the drive to improve how government appraises projects, the Treasury will be inviting Mayoral Strategic Authorities to join its Green Book Network Steering Group. This board offers independent advice on appraising in the public sector and will be scrutinising the implementation of actions set out by the review.
As well as launching the taskforce on place-based business cases, the Treasury will also review Green Book guidance on transformational change to “help public servants to assess the potential of projects to bring about transformational growth more effectively”.
The department will commission an independent review of the Green Book discount rate – which aims to support comparisons of costs and benefits occurring over time - “to make sure that the government is taking a fair view of the long-term benefits that arise from transformational investments”.
The review also responded to concerns about over-reliance on benefit-cost rations, which compare the costs and monetizable benefits of a policy, project or programme. While confirming this is “one valuable metric” for assessing business cases, the review says that the Treasury will review the Green Book to make clear it “does not endorse the use of arbitrary ‘BCR thresholds’” and that it “does not simply rank different projects, with different objectives, by their BCRs as a means of allocating funding.”
The department will also “radically simplify and shorten” the guidance contained in the Green Book and associated guides, which have all become “too long and complex”, the review says. The Treasury will “make clear the level of detail that is proportionate for business cases of different levels of cost and complexity and will publish examples of core appraisal techniques”.
The review also commits to publishing business cases for major projects, saying that “the public should be able to see the rationale behind government decision making, as well as the geographical distribution of public projects”. It adds that publishing major business cases will “help to support local and regional government by demonstrating best practice”.
The review also flagged a lack of capability and capacity to develop and assess business cases across the public sector. In response, the Treasury and the Welsh Government have committed to reform the Better Business Cases programme which provides training and accreditation in the Green Book and associated guidance. Reforms will ensure this programme provides maximum value for local and regional government participants, and HMT will also publish data on the uptake of this training in central government departments.