Eve Little, Research Impact and Engagement Manager at the UK Data Service, explains what the updated Magenta Book means for how government evaluators access and archive research data – and where the UK Data Service fits in.
On the 15th May 2026, the UK Government published an updated Magenta Book – its central guidance on government evaluation. It is a critical tool in supporting the effective development and assessment of government policies, programmes and projects.
The updated guidance references the UK Data Service as a key source of data for government evaluators.
So, what is the Magenta Book? Why does the update matter? And what does it mean for how the UK Data Service supports government evaluation?
What is the Magenta Book?
The Magenta Book is one of the government’s core analytical guidance documents, telling policy teams, analysts and commissioners across central government what good evaluation looks like. Used alongside the Green Book as a shared framework across all departments, it is explicit about its ambition:
“By embedding a culture of high quality evaluation across government, we strengthen our collective ability to learn and improve. The principles outlined in this publication will empower our professions to deliver better evidence, better decisions, and ultimately better outcomes for the public.”
The 2026 update is substantial. It introduces new guidance on value for money evaluation, test and learn approaches to policy design, and guidance on using artificial intelligence (AI) in evaluation. Throughout, it places greater weight on data: where it comes from, how to assess its quality, and how different sources can be linked together to build a fuller picture of what a policy has achieved.
Why it matters – and who is already using it
The Magenta Book is not guidance that sits on a shelf. Departments across government are already citing it as the framework underpinning their evaluation work.
The Department for Transport’s Evaluation Programme 2026 explicitly states that its overall approach to evaluation follows the guidelines set out in the Magenta Book. It covers active travel and road safety – areas where understanding what is happening on the ground depends on the kind of survey data that the UK Data Service provides access to.
We explored this recently in our blog post on how national data supports safer, stronger local communities.
The Department for Energy Security and Net Zero’s post-implementation review of the Streamlined Energy and Carbon Reporting framework and the Climate Change Committee’s A Well-Adapted UK both draw on the revised Magenta Book.
These are exactly the kinds of evaluations where longitudinal and survey data are essential – as we discussed in our blog post on how housing data through the UK Data Service helped shape the UK Government’s seventh carbon budget.
These examples are from within weeks of the updated guidance being published. As more departments align their evaluation programmes to the revised Magenta Book, that list will only grow.
Where the UK Data Service fits in
The updated guidance identifies the UK Data Service as a source of social, economic and population data that government evaluators should draw on. It is also direct about where social survey data should go, it states that:
“There should be a presumption from the outset that all survey data should be archived, if possible, commonly through the UK Data Service.”
This positions the UK Data Service as the expected home for survey data collected through government evaluation – reflecting a role that the UK Data Service has long played, and that the updated guidance now makes explicit.
Data accessible through the UK Data Service has already contributed to major government decisions. Our impact team will continue to spotlight these contributions through our Data Impact blog, case studies and impact themes that tell the bigger narrative of how data access shapes the evidence behind government decisions.
Meet the team
(Left) Finn Dymond-Green (They/Them) is the Director of Impact at the UK Data Service.
(Middle) Eve Little (She/Her) is one of the Impact and Engagement Managers at the UK Data Service.
(Right) Sophie Gawryla (She/Her) is one of the Impact and Engagement Managers at the UK Data Service.
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