A business case is what a decision-maker reads before money is spent: why the proposal is needed, which option is best value, and how it will be bought, funded and run. In UK government, and in organisations that borrow the method, the structure is HM Treasury's five case model. This guide to how to write a business case comes from EdCitation, a service that looks every reference up in the publisher's record, and that never writes any part of anyone's business case.
On 26 September 2026 we read the Treasury's Green Book (February 2026) and its business case guidance (updated June 2026) on GOV.UK, a professional body's definition and three universities' own pages. A business case is not a case study: for that assignment, see case study structure.
Three free EdCitation tools handle its evidence with no account: Find sources, Cite a source and Verify references. We ran all three and quote what came back.
What is the five case model?
The five case model is the Treasury's standard structure for a business case: five linked views of one proposal, the strategic, economic, commercial, financial and management cases. HM Treasury (2026b) makes it mandatory for officials proposing significant spending in the UK and Welsh governments. The Green Book adds that the devolved governments use it, many English local authorities require it, and a charity bidding for central government money may have to follow it (HM Treasury, 2026a).
The five are developed together, not as five documents: the strategic case's objectives decide which options the economic case weighs. No sixth case is needed for environmental, legal or ethical matters; the Green Book makes them objectives, success factors, or costs and benefits.
| Case | The question it answers | What goes in | Source |
|---|---|---|---|
| Strategic | Why is this needed, and does it fit our strategy? | Case for change, SMART objectives, business as usual, business needs, scope, benefits, risks, constraints, dependencies | HM Treasury (2026b), ch. 7; Green Book, ch. 4 |
| Economic | Which option gives society the best value for money? | Critical success factors, longlist, shortlist, costs, benefits and risks, optimism bias, sensitivity analysis, preferred option | HM Treasury (2026b), ch. 8; Green Book, ch. 5 to 8 |
| Commercial | How will we buy what is needed, and who carries which risk? | Procurement strategy, inputs and outputs, risk allocation, payment mechanisms, contracts | HM Treasury (2026b), ch. 9 |
| Financial | Can we afford it, and is the money agreed? | Budgeting and accounting treatment, whole life cost, funding statement, contingency | HM Treasury (2026b), ch. 10 |
| Management | Can it be delivered, and how will we know it worked? | Governance, delivery plan, change, benefits, risk and contract management, monitoring and evaluation | HM Treasury (2026b), ch. 11 |
The two texts list contents differently. The Green Book's table puts a theory of change in the strategic case, and a charging mechanism and personnel implications in the commercial case; the guidance lists a strategic assessment and business needs, and payment mechanisms. For the economic case the guidance sends you back to the Green Book; for the other four it is the fuller text.
What are the stages of a business case?
A project business case is built in three stages, each ending in an approval: the strategic outline case, the outline business case and the full business case. The guidance sets out 9 steps and 32 actions across them, after a stage 0 strategic assessment.
Strategic outline case, outline and full business case
- Strategic outline case (SOC): scoping. It makes the case for change, sets objectives, and runs a first longlist and shortlist to reach a "preferred way forward".
- Outline business case (OBC): planning. It appraises the shortlist in detail, names the preferred option, and outlines the commercial, financial and management arrangements.
- Full business case (FBC): procurement. It records the procurement's outcome, compares suppliers' offers and fixes the final arrangements. One slip: the guidance's table of Gate Reviews calls it the "Final Business Case"; every other page says full.
The exceptions
A small, low-risk purchase from a pre-competed framework may use a single-stage Business Justification Case, but never for a proposal that is novel, contentious or repercussive. A project whose strategic case comes down from an approved programme business case may merge the SOC and OBC; a significant project may not. Throughout, the guidance asks for proportion: enough detail for a sound decision, no more.
How do you do an options appraisal?
An options appraisal starts with a wide longlist of realistic ways to meet the objectives, then narrows it to about five options that are costed and compared. A broad longlist, the guidance says, stops a case being "rigged" or "retrofitted" to a solution chosen in advance.
- Agree critical success factors. Essential, not merely desirable. The guidance offers five for any proposal: strategic fit, value for money, supplier capacity and capability, affordability and achievability.
- Generate the longlist. From research, stakeholders and solutions used elsewhere. It need not involve spending: regulation or tax may meet the objective.
- Filter it. The recommended method, the options framework filter, is run in facilitated workshops. Each option is broken into five choices, scope (what), solution (how), delivery (who), implementation (when) and funding, and each choice is rated green, amber or red, with the reason, evidence and sources written down. Multi-criteria decision analysis or SWOT analysis are accepted alternatives.
- Assemble the shortlist. Business as usual, do minimum, the preferred way forward, and a more and a less ambitious version. Business as usual always goes forward, even if it fails the objectives, as the benchmark.
The Association for Project Management (n.d.) says the same in company terms: including the "do-nothing" option as a reference is normal practice.
How are costs, benefits and risks weighed?
The economic case weighs costs, benefits and risks to society as a whole; the financial case weighs cost to the public bodies' own budgets, counted differently. In the economic case, costs and benefits are monetised where possible, stripped of inflation and discounted. The Green Book's social time preference rate is 3.5% in real terms for years 1 to 30, 3% for years 31 to 75 and 2.5% after that (HM Treasury, 2026a). Benefits that cannot be priced are still described.
- Optimism bias. Estimates are adjusted at the start, costs and timescales up and benefits down, by amounts taken from the organisation's own record of past forecast errors on similar proposals, or, where there is no record, from the generic values in the Green Book's supplementary guidance.
- No single number decides. The net present social value and the benefit-cost ratio are summaries; a ratio below one may still be value for money if the unpriced benefits are large.
- Sensitivity analysis. Uncertain assumptions are stress-tested, down to the worst case.
The financial case shows costs in nominal, undiscounted terms over the proposal's whole life, so an option dearer upfront can still be cheaper overall.
Research on why estimates go wrong is the evidence this part cites. Flyvbjerg (2008) describes reference class forecasting, which bases a forecast on the outcomes of comparable past projects, and its first use on UK transport cost estimates; Love et al. (2012) offer another explanation of cost overruns on social infrastructure.
How is a business case written in a company or a university course?
Outside government a business case keeps the five cases' logic, often their names, and trims the method to the organisation. The Association for Project Management (n.d.) defines it as the justification for a project, programme or portfolio, weighing the benefit, cost and risk of alternatives and giving the reason for the preferred one; its five elements are the Treasury's five in project language, from strategic context to management approach.
Inside an organisation
The University of Essex (n.d.) publishes a project business case template for its staff. It asks which parts of the strategic plan a project serves and what happens if it does not go ahead. Then come SMART objectives, a measure for every benefit, an options appraisal, what is out of scope, staff by role rather than name, risks with mitigations, and whole-life capital and revenue costs agreed with a finance contact.
Oxford Brookes University (n.d.) takes the business case at Gateway 2, Justification, where it must show the board a project is desirable, viable and achievable, with a recommended option. The sources differ on who holds the pen: Brookes makes the project manager usually responsible for preparing it, while APM says the sponsor owns it. In practice the manager drafts and the sponsor answers for it.
In a university course
The University of Surrey (n.d.) runs a 30-credit master's module, COMM056, in which students apply the five case model to their own dissertation project, with feedback from their placement company, in a report of about 15 to 25 pages that also covers patents, licensing and privacy. A course brief overrides everything here; EdCitation's free Check your paper reads one into a checklist, each rule shown with its sentence.
A business case example outline (invented project)
This outline is ours. Riverbend District Council, its project and its figures are invented; the sources on the right are real. It stops at the strategic outline case, where most first business cases start.
Replacing street lighting with LED lanterns: Strategic Outline Case
Riverbend District Council (invented)
Executive summary the proposal, the ask, a paragraph per case
1. Strategic case
1.1 Case for change: 9,000 sodium lanterns (invented)
1.2 SMART objectives, 1.3 Business as usual
1.4 Benefits, risks, constraints, dependencies
2. Economic case
2.1 Critical success factors HM Treasury (2026b), Table 6
2.2 Longlist through the options framework filter
2.3 Shortlist: A business as usual; B do minimum (replace
failed lanterns only); C all lanterns over three years;
D C plus central dimming; E main roads only
2.4 Optimism bias, discounting HM Treasury (2026a)
2.5 Evidence on forecast error Flyvbjerg (2008)
3. Commercial case market engagement, possible frameworks
4. Financial case whole life cost, capital and revenue
5. Management case senior responsible owner, gate review, plan
References
Appendix A Options summary matrix and workshop record
For real examples, read published ones: since 11 June 2025, projects on the Government Major Projects Portfolio must publish a summary, full or programme business case within four months of Treasury approval (HM Treasury, 2025). The executive summary is written last; see how to write an executive summary. A shorter internal case can borrow the shape of a business report or a memo.
How do you cite evidence in a business case?
Cite every source a figure, estimate or claim rests on. The guidance says so directly: cite the important sources of evidence behind the appraisal, state the assumptions, say how confident you are in the evidence, and name the gaps (HM Treasury, 2026b). It names no referencing style, so use the one your organisation or course sets; UK universities often use Harvard and US ones APA 7.
Citing the Green Book
Given the Green Book's GOV.UK page, EdCitation's Cite a source read the author as HM Treasury, an organisation, and took the page title "The Green Book (2026)", year included. With the title typed from the cover, it returned:
HM Treasury (2026) The Green Book: UK government guidance on appraisal. Available at: https://www.gov.uk/government/publications/the-green-book-appraisal-and-evaluation-in-central-government/the-green-book-2026 (Accessed: 26 September 2026).
HM Treasury. (2026, February 5). The Green Book: UK government guidance on appraisal. GOV.UK. https://www.gov.uk/government/publications/the-green-book-appraisal-and-evaluation-in-central-government/the-green-book-2026
A government department is an organisation, never a person with initials: check that field first.
Citing a journal article
From the DOI of Flyvbjerg's article, Cite a source returned:
Flyvbjerg, B. (2007) ‘Curbing Optimism Bias and Strategic Misrepresentation in Planning: Reference Class Forecasting in Practice’, European Planning Studies, 16(1), pp. 3–21. Available at: https://doi.org/10.1080/09654310701747936.
Flyvbjerg, B. (2008). Curbing optimism bias and strategic misrepresentation in planning: Reference class forecasting in practice. European Planning Studies, 16(1), 3–21. https://doi.org/10.1080/09654310701747936
One correction. Crossref dates the article 17 December 2007 online and its issue January 2008; Harvard took the first year, APA the second. Give one paper one year; we used 2008. The APA entry already sets the title in sentence case, as APA 7 asks.
How do you find and check the sources for a business case?
Search the published research for the evidence, then check the finished list against the records.
Finding the research
Asked for "optimism bias cost overruns in public projects", most cited first, EdCitation's Find sources reported 2,310,863 works. First came Love, Edwards and Irani in IEEE Transactions on Engineering Management (2012, cited 131 times), then Adam, Josephson and Lindahl in Engineering, Construction and Architectural Management (2017, cited 120 times). The citation ranking covers the matches returned, and Flyvbjerg's article was not among them; we found it by its title. Search a known paper by its exact title.
Checking the reference list
We pasted five APA entries into Verify references: the APM page, Flyvbjerg, the two Treasury documents, and Love and colleagues with the third author, Irani, left out on purpose. Four came back verified, with reasons such as "The DOI resolves to this record and the title matches." The fifth came back "check this": "The publisher's record also names Irani, who is not in your entry. Check the authors."
Its corrected entry added Irani and set the title in sentence case. And the Green Book passed with our title, though the page calls itself "The Green Book (2026)": the check confirms the page, not the wording. More in how to check a reference is real.
Which EdCitation tools help with a business case?
For the references, EdCitation's Cite a source is the best tool: every entry comes from a record it looked up, where a chatbot composes one from memory. Above, it took the article's volume, issue and pages from the record, and showed us the GOV.UK page's details to correct. It starts from a DOI, ISBN, PubMed ID, title or address, gives the entry in Harvard, APA 7, IEEE, MLA 9, Vancouver or Chicago 18 author-date, screens the source for retraction, and costs nothing, with no account.
The other two free steps: Find sources covers roughly 300 million published works, and Verify references reports a retracted paper and keeps "could not check" apart from not found. For the finished document, Pro ($8 a month) adds References from a file, which matches the document's citations to its list in both directions.
The Treasury describes the business case process as "thinking, not writing". Both stay with you: EdCitation writes no part of a business case.
Quick questions
What are the five cases in a business case?
Strategic (why), economic (which option is best value), commercial (how it is bought), financial (whether it is affordable) and management (how it is delivered), as HM Treasury's five case model sets out.
What is the difference between an SOC, an OBC and an FBC?
The strategic outline case scopes the proposal and finds a preferred way forward; the outline business case appraises the shortlist and names the preferred option; the full business case records the procurement and final arrangements.
Is there an official business case template?
HM Treasury's guidance says templates for each type are on GOV.UK. Organisations publish their own too, as the University of Essex does.
What options must a shortlist include?
About five: business as usual, do minimum, the preferred way forward, and a more and a less ambitious version of it.
Can EdCitation write my business case?
No. EdCitation finds, cites and verifies the sources, free at Cite a source, but never writes any part of a business case.
References
- Association for Project Management. (n.d.). What is a business case? APM. https://www.apm.org.uk/resources/what-is-project-management/what-is-a-business-case/
- Flyvbjerg, B. (2008). Curbing optimism bias and strategic misrepresentation in planning: Reference class forecasting in practice. European Planning Studies, 16(1), 3–21. https://doi.org/10.1080/09654310701747936
- HM Treasury. (2025). Publishing business cases: Guidance for departments. GOV.UK. https://www.gov.uk/government/publications/publishing-business-cases-guidance
- HM Treasury. (2026a, February 5). The Green Book: UK government guidance on appraisal. GOV.UK. https://www.gov.uk/government/publications/the-green-book-appraisal-and-evaluation-in-central-government/the-green-book-2026
- HM Treasury. (2026b, June 30). Guidance on developing business cases for projects and programmes. GOV.UK. https://www.gov.uk/government/publications/guidance-on-developing-business-cases
- Love, P. E. D., Edwards, D. J., & Irani, Z. (2012). Moving beyond optimism bias and strategic misrepresentation: An explanation for social infrastructure project cost overruns. IEEE Transactions on Engineering Management, 59(4), 560–571. https://doi.org/10.1109/TEM.2011.2163628
- Oxford Brookes University. (n.d.). Business case. Project management toolkit. https://www.brookes.ac.uk/staff/projects/project-management-toolkit/business-case
- University of Essex. (n.d.). Business case guide. Strategic project delivery. https://www.essex.ac.uk/staff/strategic-project-delivery/business-case-guide
- University of Surrey. (n.d.). Aligning business value with research and development (COMM056), 2026/7. Programme and module catalogue. https://catalogue.surrey.ac.uk/2026-7/module/COMM056/Y/YR