Five Case Model

The five case model organizes a business case into linked strategic, economic, commercial, financial, and management perspectives. HM Treasury’s Green Book uses it for public proposals. The perspectives are developed together, with detail proportionate to the stage, cost, complexity, and risk.

• Strategic: explain the need, objectives, theory of change, strategic fit, and future business-as-usual baseline.
• Economic: compare options and identify value for money, including costs, benefits, uncertainty, and effects that cannot be monetized.
• Commercial: explain sourcing, supplier capability, service requirements, contractual arrangements, and risk allocation.
• Financial: establish affordability, funding, and the timing of expenditure, income, and balance-sheet effects.
• Management: establish governance, staffing, delivery and change plans, risk management, benefits realization, monitoring, evaluation, and contingencies.

Value and affordability are different. An option can promise worthwhile outcomes but lack funding at the required time; an affordable option can offer poor value. Commercial and management evidence can also change the economic comparison by exposing an unavailable supplier or an unrealistic delivery assumption. Special concerns such as security or environmental effects belong within the relevant objectives, conditions, and appraisal, rather than requiring a disconnected sixth case.

Using the model in a technology decision

A company can borrow these questions, but should state whose outcomes and costs it evaluates. A corporate cash return is not the same as public social value. The framework also does not require every early exploration to have final contract details. The Green Book distinguishes strategic outline, outline, and full business cases; evidence and commitments become more specific as the decision progresses. Early funding still needs credible bounds and explicit gaps.

In a fictional claims-engine proposal, the deck contained architecture, vendor information, migration phases, staffing, and risks. Those fragments had not been connected into a comparison, funding plan, supported delivery arrangement, and exact request. The missing request was a separate defect; it did not prove that financial or management information was entirely absent. Forty Slides and No Ask develops a bounded pilot request and the later procurement decision. optimism bias explains evidence-based forecast corrections, while switching value examines boundaries in a defined comparison. Neither replaces the five perspectives.

References

• HM Treasury, The Green Book, 2026 edition, chapter 3, Tables 2–3.