The Five Case Model for Smarter Public Investment

Across the world, governments are under pressure to deliver more with less. Public finances are stretched, scrutiny is intense, and the expectations of citizens are higher than ever. Against this backdrop, sound investment decision-making is no longer a “nice to have”, it is essential. The Five Case Model (FCM), which I had the privilege to develop and refine during my career in the UK Treasury and subsequently in advisory work across the globe, provides a tried and tested framework for doing just that.

At its core, the Five Case Model is about asking the right questions, at the right time, in the right order. It offers a practical, structured approach for developing, appraising and delivering business cases that are robust, evidence-based and aligned to strategic goals. Since its inception in the UK, it has become the de facto standard for public sector investment planning in numerous countries. In this article, I’ll explain what the model is, how it works, who is using it, and why it has stood the test of time.

The Five Case Model (FCM) is the UK Government’s best practice framework for preparing business cases. It is the standard across Whitehall and devolved administrations, embedded in HM Treasury’s Green Book and required for all major spending proposals.

At its heart are five interrelated “cases”, each representing a critical dimension of a successful intervention:

1. Strategic Case – Is there a compelling case for change?
2. Economic Case – What is the best value for money option?
3. Commercial Case – Can a deal be done?
4. Financial Case – Is the proposal affordable?
5. Management Case – Can the proposal be delivered successfully?

Each case represents a different lens through which the proposal is tested. The model ensures that initiatives are not only desirable in principle but also feasible, viable and deliverable in practice. It is designed to support evidence-based decision-making throughout the project lifecycle, from early concept through to evaluation.

The Five Case Model emerged in the early 2000s, drawing on lessons from decades of public sector investment, both the good and the not-so-good. It sought to address persistent challenges in public expenditure:

• Projects were too often commissioned on political whim, with little thought to delivery.
• Value for money was rarely tested rigorously.
• Risks and affordability were afterthoughts.
• There was little consistency in business case development.

As Head of Investment Policy  and Appraisal at CCTA, HM Treasury, I worked with colleagues to develop a practical framework that would instil discipline, transparency and accountability into the decision-making process. The model was built not from theory, but from the realities of government. It was shaped through trial, feedback and iteration across a range of sectors, from transport and health to defence and digital.

We designed the Five Case Model to be:

• Simple but rigorous – accessible to non-specialists but underpinned by robust analytical techniques;
• Iterative – developing over three stages: Strategic Outline Case (SOC), Outline Business Case (OBC), and Full Business Case (FBC);
• Modular – able to scale to suit the size and complexity of the proposal;
• People-focused – not just about numbers, but about clarity, consensus and collaboration.

This is the foundation. It answers the fundamental question: Why are we doing this? It sets out:

• The rationale for intervention;
• Strategic alignment with local, regional or national priorities;
• Clear spending objectives;
• Evidence of need and market failure;
• The scope of the proposal.

This case should win hearts and minds. If this is not strong, the rest doesn’t matter.

The economic case assesses the options for achieving the desired outcomes and identifies the one that offers the best social value. It involves:

• Longlisting and shortlisting of options;
• Use of cost-benefit or cost-effectiveness analysis;
• Consideration of risks, optimism bias, distributional impacts, and unquantifiable benefits.

This is the analytical heart of the model, ensuring resources are used wisely.

This case assesses whether a viable deal can be secured and maintained. It considers:

• Procurement strategy;
• Risk transfer and contractual structure;
• Supplier appetite and capability;
• Commercial dependencies and legal issues.

The focus is on securing the best outcome from suppliers while managing risks appropriately.

This sets out whether the project is affordable and how it will be funded. It includes:

• Budget availability;
• Cash flow forecasts;
• Impact on departmental spending limits;
• Accounting implications and contingencies.

No proposal should proceed without a clear funding strategy.

Finally, this case describes how the project will be successfully delivered. It outlines:

• Governance and assurance;
• Project planning and resourcing;
• Risk management and benefits realisation;
• Evaluation arrangements.

It ensures the organisation has the capability and plan to make it happen.

The model evolves through three stages:

• Strategic Outline Case (SOC) – establishes the strategic fit and sets direction.
• Outline Business Case (OBC) – develops options in detail and sets the commercial and financial framework.
• Full Business Case (FBC) – finalises the deal, confirms affordability, and signs off delivery plans.

This phased approach supports early decision-making while maintaining flexibility and control.

While rooted in UK Treasury guidance, the Five Case Model has become an international standard.

• HM Treasury requires FCM for all major spending proposals.
• Cabinet Office, Department for Transport, NHS England, and all devolved administrations (Scotland, Wales, Northern Ireland) mandate or endorse its use.
• It is embedded in local government assurance processes, especially for City Deals, Levelling Up, and Combined Authorities.

The model has been adopted or adapted by governments and institutions across the globe:

• New Zealand: The Treasury has formally adopted the FCM in its Better Business Cases programme, with guidance adapted for local context.
• Ireland: The Department of Public Expenditure and Reform uses a version of the model in its Public Spending Code.
• South Africa, Malaysia, and parts of Latin America have integrated the FCM into capacity-building efforts supported by the World Bank and OECD.
• Multilateral bodies including the World Bank, IMF, UNDP, and Asian Development Bank draw on the model in training and advisory support.

Its appeal lies in its pragmatism. Unlike many frameworks that focus solely on economic appraisal or governance, the FCM bridges strategic intent, value, procurement, finance, and delivery in one coherent structure.

The model delivers benefits to multiple stakeholders across the public sector landscape:

1. For Ministers and Senior Leaders

• Clarity: A single, structured document that tells the full story.
• Assurance: A consistent basis for scrutiny, decision and approval.
• Alignment: Confidence that proposals support wider strategic goals.

2. For Project Teams and Analysts

• Guidance: A clear roadmap for developing cases.
• Integration: Brings together policy, economics, finance, procurement and delivery.
• Credibility: Proposals are more likely to be approved and funded.

3. For Citizens and Taxpayers

• Transparency: Decisions can be explained and justified.
• Value for Money: Projects are selected and designed with benefits in mind.
• Confidence: A sense that public funds are being used wisely.

4. For International Partners

• Adaptability: Can be tailored to local institutional contexts.
• Capacity Building: Promotes good governance and accountability.
• Results Orientation: Keeps the focus on real-world benefits.

Let me address a few myths that occasionally surface.

• “It’s bureaucratic.” On the contrary, the model prevents box-ticking by requiring real thought. Done properly, it streamlines decision-making by preventing costly mistakes later.
• “It’s only for big projects.” The model is scalable. We’ve used it for everything from £1 billion infrastructure schemes to £250,000 innovation pilots.
• “It’s just about getting funding.” FCM isn’t a sales pitch, it’s a decision support tool. It should be used to test, challenge and refine ideas, not just justify them.

Over two decades, I’ve seen the Five Case Model used in every conceivable setting – to plan new hospitals, digitise public services, fund major rail upgrades, and design cross-border aid programmes. What I’ve learned is this:

• A good business case is never about paperwork, it’s about better decisions.
• The best projects aren’t those with the slickest presentations, but those with the clearest thinking.
• Success lies not in the spreadsheet, but in the conversations that the model prompts – about purpose, value, and deliverability.

The Five Case Model isn’t perfect. But in a world where public trust in institutions is fragile, and the cost of failure is high, it offers a framework for rigour, discipline and transparency. And that, in my view, is priceless.

If you are working in or with government, and you want your proposal to succeed, use the Five Case Model. It doesn’t guarantee approval, but it does guarantee that your idea will be tested thoroughly, fairly and consistently. And if it survives that process, it’s probably worth doing.

For countries seeking to build investment capacity, for departments under scrutiny to demonstrate value, and for delivery teams striving to implement change, this model delivers.

More than a framework, the Five Case Model is a mindset. One that says: we spend public money as if it were our own. Because in the end, it is.

HM Treasury. (2022). The Green Book: Central Government Guidance on Appraisal and Evaluation. London: HM Treasury.
New Zealand Treasury. (2021). Better Business Cases Guidance. Wellington: NZ Government.
OECD. (2015). Public Investment and Good Governance. Paris: OECD Publishing.
World Bank. (2020). Better Spending for Better Lives: How Latin America and the Caribbean Can Do More with Less. Washington, DC: World Bank.