The 2026 update to the Magenta Book represents the most significant shift in government evaluation standards since 2020, moving the needle from “measuring what happened” to “learning how to improve in real-time.”
Led by the Evaluation Task Force (ETF), the update to Magenta Book, the UK government’s central guidance on evaluation, is a significant milestone for evidence-based policymaking in the UK.
For every civil servant, regardless of your role, adopting the principles of the Magenta Book is crucial for ensuring that government is driven by rigorous evidence, guaranteeing that taxpayer money is spent effectively.
This update ensures that the guidance reflects the advances in evaluation practice since the previous 2020 version. The revised Magenta Book introduces several new and significantly expanded areas of focus to support high-quality evaluation across government. This includes
- Value for Money (VfM) A redrafted section and new annex provide a clearer definition and expanded methodologies for assessing the best use of public resources, including non-monetisable social costs and benefits.
- Test and Learn A dedicated new annex positions “Test and Learn” as a way of working that uses social research to iteratively adapt and optimize interventions before full-scale impact assessment.
- Evaluation and Benefits Management New content clarifies the complementary relationship between these two disciplines, distinguishing the systematic approach to assessment used in evaluation from project delivery focused benefits management approaches.
- Research Transparency The update incorporates new principles for transparency, including recommendations for pre-registering evaluation protocols and using open-source platforms like GitHub for sharing code.
- AI in evaluation New guidance addresses the responsible and ethical use of Artificial Intelligence (AI) in social research and evaluation.
- Place-Based Evaluation A new section offers specific considerations for evaluating interventions designed for particular geographic areas.
A Collaborative Effort
The update was led by the Evaluation Task Force in collaboration with volunteers across government, including representatives from the Cross-Government Evaluation Group (CGEG) and departmental Heads of Profession. The process included extensive stakeholder engagement and a robust quality assurance, including external peer review.
The updated Magenta Book continues to align with HM Treasury’s Green Book, ensuring consistency between policy appraisal and subsequent evaluation. This update ensures our guidance remains comprehensive and effective to deliver better outcomes for the public through robust, evidence-based decision-making.
The full Updated Magenta Book is now available on GOV.UK.
