HM Treasury has launched a new Green Book to support fairer and more balanced public investment decisions across the UK.

The new guidance will support fairer and more balanced decisions on investment in every part of the country, including outside London and the South East and across urban, rural and coastal communities.

The Green Book is a UK government guidance document from HM Treasury that sets out the framework for appraising and evaluating policies, projects and programmes, focusing on costs, benefits, and risks.

Parts of the UK have lagged behind others when it comes to public investment. Ater years of unfair allocation of spending and the new guidance will give all areas a “fair hearing”, so that every region can realise its full potential and thrive economically.

The revamped Green Book comes after the prime minister announced 40 new areas across England will be able to decide where up to £20m is invested in their neighbourhood, through a new £800m package that will restore pride into local communities and breathe new life into high streets, save much-loved community spaces and bring people together through local events and activities.

The new Green Book makes sure that investment decisions are no longer based solely on single metrics such as benefit-cost ratios, and that these metrics are not wrongly used to compare investment choices across different regions or between urban, rural and coastal communities. Instead, decisions must take into account the full range of impacts of different investment options, giving a fair hearing to every part of the UK.

Chancellor Rachel Reeves said: “For too long, people outside of London and the South East will have felt the system is working against them and their community, not for them. I know full well that everyone has the potential to contribute to our country’s growth and success regardless of where you live.

“These groundbreaking reforms are part of a new approach from the Treasury that truly makes a long-lasting difference for all areas across the country – ensuring they get the fair hearing they deserve and can have confidence in how government invests into where they live.”

The new Green Book still recognises the importance of robust evidence and analysis, and metrics like benefit-cost ratios – but is clear these must not be used as a crude pass/fail test. Ministers will now see a more rounded assessment of a proposal’s impacts, rather than being guided by one headline number.

The new guidance has been developed hand-in-hand with devolved administrations, mayoral combined authorities and local councils, and supports the aim of this government to change the way the state makes decisions: promoting decision making that supports higher, more productive and more balanced growth across the whole of the United Kingdom.

Following the Green Book Review 2025, which found the old Green Book was too long and too complex, the new version is also clearer, more accessible and more than 40% shorter than the previous version. This new guidance will save public servants time so they can get on with their jobs delivering for the public.

Tracy Brabin, Mayor of West Yorkshire, said: “Having a simpler and more accessible Green Book will help to drive investment and open opportunity across the country.  The changes provide great clarity and certainty, making it easier for places like West Yorkshire to grow and succeed.”

The Association for Consultancy and Engineering (ACE) welcomed the announcement. The organisataion has long argued that a stronger, clearer, place-based business case is essential to addressing historic underinvestment and ensuring that regions outside London and the South East receive a fair hearing when public investment decisions are made.

Ben Brittain, director of public affairs, said: “This is exactly the direction of travel ACE has been calling for. If we’re serious about growth, we must be serious about place. A strong, place-based business case isn’t a nice-to-have – it’s mission-critical to unlocking investment, jobs and opportunity in every region.

“By giving all parts of the country a fair hearing, the new Green Book puts common sense back at the heart of decision-making and creates the conditions for locally-led growth that people can actually see and feel.”

Click here for more details of the new Green Book.