By James Collis (UK Cabinet Office) and Julian King (public policy consultant and evaluation specialist)
The refreshed Green Book and Magenta Book provide clearer, more consistent guidance on making balanced value-for-money judgements across the policy cycle. The Value for Investment approach offers a practical way to implement those principles, using transparent reasoning, mixed methods, and stakeholder engagement.
The UK government has updated two key guidance books for policy development that are influential internationally: the Green Book for appraisal and the Magenta Book for evaluation. Together, they provide a clearer and more consistent framework for developing, testing and reviewing public spending proposals across the policy cycle.
One of the most useful features of the refresh is the shared emphasis on balanced, evidence-based judgement. The 2026 Green Book defines value for money (VfM) as a “balanced judgement about the optimal use of public resources to achieve the objectives of a proposal”. It makes clear that this judgement must consider costs and benefits that cannot be easily valued in monetary terms as well as those that can, together with public sector financial impacts, distributional effects, risk, and uncertainty. The updated Magenta Book carries that logic into evaluation, where VfM evaluation asks whether an intervention has been a good use of resources, in light of what was achieved, for whom, how, why and at what cost.
The scale of this agenda is increasingly visible in practice: when the Government’s Evaluation Registry was launched publicly in March 2025, it already included information on over 200 VfM evaluations. In a little over a year, this has doubled to 450. The trend is even more striking looking at the pipeline. Just 15% of previously completed evaluations on the Registry include a VfM evaluation. That figure now stands at 40% with VfM evaluation for ongoing evaluations and 60% for planned evaluations – a fourfold increase compared to the historic figure.
This is a welcome development. The emphasis on balanced value judgements recognises that good public decisions cannot be reduced to a single number, however useful summary metrics may be. Benefit-cost ratios, cost-effectiveness ratios and other quantitative indicators remain important, but they need to sit within a broader account of public value, delivery, evidence quality and uncertainty.
This is where Value for Investment (VfI) can make a practical contribution. The VfI approach complements the Green Book and Magenta Book by offering a structured way of helping practitioners apply the spirit of the guidance in real-world settings, especially where evidence is mixed, outcomes are diverse, and some important dimensions of value cannot readily be valued monetarily.
A more joined-up view of value
The Green Book is primarily concerned with appraisal: assessing the costs, benefits and risks of different options before decisions are made. The Magenta Book is concerned with evaluating the processes, outcomes and value of policies, programmes and projects once they are implemented, and what can be learned for future decisions.
In practice, these tasks are closely connected. Appraisal sets out the case for action. Evaluation then tests how far those expectations were realised. That connection is especially important for value for money. A VfM appraisal asks whether a proposal is expected to represent a good use of public resources. A VfM evaluation asks whether it actually turned out to be a good use of resources, and what can be learned for future choices. The VfI approach helps join these questions together by making the evaluative logic explicit from the start.
The key idea is simple: if VfM is a balanced judgement, then practitioners need a transparent way to make that judgement. They need to define what matters, agree how good performance will be recognised, gather fit-for-purpose evidence, and show how the evidence supports the conclusion reached.
Interdisciplinary work, integrated work streams
Both the Green Book and the Magenta Book now point towards a more interdisciplinary way of working. Appraisal and evaluation require economic analysis, evaluation design, delivery insight, policy knowledge, financial understanding, data expertise and, where appropriate, the perspectives of users, communities and partners.
VfI is designed for exactly this kind of work. It brings together economic and evaluative thinking, rather than treating them as separate or competing traditions. Cost-benefit analysis, cost-effectiveness analysis and other economic methods can provide crucial evidence. VfI places them within a wider evaluative frame that also considers stewardship of resources, productive delivery, equity, context, uncertainty, and the values of different stakeholders.
This matters because many public interventions create value in ways that are only partly captured in monetary terms. Some benefits are intangible, long term, preventative, relational or unevenly distributed across places and groups. A purely monetised account may still be informative, but it may not be sufficient for a balanced judgement.
The updated Magenta Book recognises this in its set of principles for VfM evaluation. These centre on strong links between VfM evaluation and appraisal; coherence between VfM, process and impact evaluation; and building from empirical data to ensure that monetisable findings are interpreted in the context of a broader set of evidence. VfI provides a practical structure for bringing those strands together, so that VfM is informed by evidence from across the evaluation, rather than bolted on at the end.
Mixed methods as a strength, not a compromise
The new guidance is also clear that different questions require different methods. The Magenta Book and its extra methodological guidance (Annex A) set out a broad range of approaches. These include theory-based impact evaluation, experimental and quasi-experimental methods, cost-benefit analysis, cost-effectiveness analysis, social return on investment, Four Es frameworks, rubric-based approaches, synthesis methods, interviews, focus groups, case studies, surveys, monitoring data and consultative or deliberative methods.
This breadth is important. It avoids the unhelpful idea that there is one “best” method for all evaluation questions. Instead, it invites practitioners to choose methods that are fit for purpose: appropriate to the intervention, the decision context, the available data, the maturity of delivery and the kinds of value at stake.
VfI works in the same way. Rather than prescribing a single method or a fixed hierarchy of evidence, it asks what evidence is needed to make a credible judgement against agreed criteria, and then uses the most appropriate mix of methods to answer that question.
That might include a cost-benefit analysis where benefits and costs can be reasonably monetised. It might include a cost-effectiveness analysis where the objective is clear but monetisation is not appropriate. It might include process evidence to understand delivery, qualitative research to understand experience and context, impact evidence to test contribution or attribution, and distributional analysis to understand who benefited and who did not.
The point isn’t to collect every possible form of evidence, but rather to collect the evidence needed to support a defensible judgement. Mixed methods are valuable because they allow practitioners to examine a proposal or intervention from more than one angle, and to explain the story behind the numbers.
Making judgement visible
Perhaps the most important shared theme is transparency in judgement. The Green Book emphasises balanced appraisal drawn from clear evidence and assumptions. The Magenta Book emphasises useful, credible, robust and proportionate evaluation, with openness and transparency across planning, analysis and reporting.
This is an area where VfI is particularly well aligned. The backbone of the approach is the use of explicit criteria and performance standards, often expressed through rubrics. A rubric sets out what matters and what different levels of performance look like, for example what would count as excellent, good, adequate or poor value in a particular context.
Explicit criteria and standards provide a bridge from the evaluation to its practical use in policy making. They push the evaluation findings off the fence. Rather than a busy policy maker wading through an evaluation to reach their own conclusions in a hurry, evaluative judgements are shown upfront with transparent reasoning – including the strengths and limitations of the evidence.
Rubrics do not replace data. They sit alongside, providing a transparent framework to guide the selection of evidence and methods, interpretation of evidence, and making evaluative judgements. This is especially useful when evidence is mixed, when some outcomes can be valued monetarily and others cannot, or when different stakeholders place value on different things.
The Magenta Book Annex A now explicitly includes rubrics as one of the tools for VfM evaluation. It describes rubrics as a structured set of criteria and performance standards, usually co-designed early with evaluators and stakeholders, to provide a clear basis for integrating quantitative and qualitative evidence into an overall value for money judgement. That is very close to the practical logic of VfI, which treats the heart of evaluation as reasoning carefully from agreed criteria and standards to reach conclusions from credible evidence that are transparent and open to scrutiny.
Stakeholder engagement that strengthens judgements
The refreshed guidance also places appropriate weight on stakeholder needs and use. The Magenta Book describes good evaluation as tailored around the needs of stakeholders, including decision makers, users, implementers and the public. It also recognises that stakeholder engagement can improve understanding, build stronger relationships and increase the likelihood that evaluation findings are used.
VfI treats stakeholder engagement as an integral part of the evaluative endeavour, not as a separate communications exercise. Stakeholders can help define what value means in context, identify important forms of evidence, test whether the theory of change is plausible, and interpret findings in light of delivery realities.
This doesn’t mean that every judgement becomes a matter of preference or negotiation. On the contrary, well-designed participation can make judgement more disciplined. It helps surface assumptions, clarify trade-offs and make explicit why some dimensions of value matter more in a particular context.
This is particularly relevant for place-based, relational or complex interventions. In these cases, the people closest to delivery and experience may understand mechanisms, constraints and unintended effects that are not visible in administrative data alone. Their perspectives can strengthen both appraisal and evaluation, provided they are gathered and used systematically.
A practical scaffold for implementation
Many practitioners already know that balanced judgement, mixed methods and stakeholder engagement are desirable. The challenge is how to do these things in a way that is proportionate, systematic and useful for decision making. VfI offers a practical scaffold for implementing these principles. In broad terms, it involves the following eight steps:
This sequence aligns naturally with the emphasis on balanced value for money judgements set out in both the Green Book and Magenta Book updates.
Using this process, VfI can be implemented across whole organisations to navigate different contexts and requirements. The framework is designed to be applied at different levels of scale, from individual interventions to organisation-wide portfolios. A major national programme may need a substantial VfI framework, multiple methods and extensive engagement. A smaller local intervention may need a lighter version, with a narrower set of criteria, a proportionate evidence plan and a simpler rubric. Rubrics can be developed once at portfolio level and applied across multiple similar programmes, enabling like-with-like comparison while maintaining contextual responsiveness. The same principles apply in each case: the judgement should be explicit, based on credible evidence, proportionate, and useful.
Complementing the wider methods set out in the Magenta Book
It is important to be clear about what VfI is, and what it is not. VfI is not a single analytical method in the same sense as cost-benefit analysis, difference-in-differences or contribution analysis. Nor is it a substitute for good evaluation design, good data or appropriate economic analysis.
Rather, VfI is a wrap-around framework for bringing evidence and values together to answer value for money questions. It can be used alongside any of the methods set out in the Magenta Book. It helps practitioners decide how those methods contribute to an overall judgement about resource use, and it helps them combine multiple pieces of evidence:
This combination is often what rigour requires when decisions are complex and the evidence base is necessarily varied. The discipline lies in being explicit about the judgement being made, the standards being applied, the evidence being used and the uncertainty that remains.
Supporting test, learn and adapt
The refreshed Magenta Book also gives more prominence to evaluation as part of policy design, development and delivery. Its inclusion of Test and Learn guidance is consistent with a view of evaluation as something that supports improvement as well as accountability.
VfI can support this way of working. When criteria and standards are developed early, they can inform design choices, monitoring systems and learning questions during implementation. They can help teams ask not only whether an intervention is on track, but whether it is still likely to represent a good use of resources as circumstances change.
This is valuable in uncertain environments. Public programmes often operate in changing contexts, with evolving delivery conditions, emerging evidence and shifting needs. A transparent VfI framework can help teams revisit assumptions, test whether the value proposition still holds, and adapt without losing sight of the original objectives.
In this sense, VfI is more than a reporting tool. It is also a learning tool, helping teams connect appraisal assumptions, implementation evidence and evaluation findings over time.
From guidance to good practice
The refreshed Green Book and Magenta Book provide a clear opportunity to strengthen the way VfM is understood and assessed in UK public policy. They support a view of VfM as a balanced judgement, grounded in evidence and attentive to objectives, costs, benefits, risks, uncertainty, distributional effects and learning.
Value for Investment offers one practical way to support that ambition, throughout the policy cycle. It helps practitioners move from principle to practice by making the judgement process explicit, combining methods appropriately, engaging stakeholders constructively and integrating evidence across appraisal and evaluation.
The result is not a more complicated version of value for money. It is a clearer one. It recognises that public value is often multi-dimensional, that evidence is often mixed, and that judgement is unavoidable. The task is therefore to make that judgement as transparent, credible and useful as possible.
That is the promise of the refreshed guidance. VfI can help realise it.
References
HM Treasury (2026) The Green Book: UK Government Guidance on Appraisal. London: HM Treasury.
HM Treasury (2026) The Magenta Book: Central Government Guidance on Evaluation. London: HM Treasury.
HM Treasury (2026) Magenta Book Annex A: Analytical Methods for Use within an Evaluation. London: HM Treasury.
King, J., Wate, D., Namukasa, E., Hurrell, A., Hansford, F., Ward, P., Faramarzifar, S. (2023) OPM’s Approach to Assessing Value for Money. Oxford: Oxford Policy Management.
King, J. and Hurrell, A. (2024) A Guide to Evaluation of Value for Money in UK Public Services. London: Verian Group.