Why Good Business Cases Fall Apart Under Scrutiny
A business case is not a sales pitch. It is the document a funder, board, or auditor returns to when the project is over budget, behind schedule, or under question. If it was built to win approval rather than to withstand examination, the gap shows the moment someone asks a hard question. In the spring of 2022, with material prices climbing, trades in short supply, and supply chains still unsettled, that scrutiny got sharper: approvers wanted to know which numbers were real and which were hope.
Most weak business cases fail in predictable ways. Knowing the pattern is half the cure.
The mistakes that sink a business case
Treating one option as the whole analysis. If the only choice presented is "do this project," reviewers cannot tell whether it is the best use of money. A credible case compares the preferred option against doing nothing and against at least one realistic alternative, and explains why the recommendation wins.
Costing the build but not the life. Teams price construction or implementation and stop there. They omit operating costs, maintenance, staffing, and eventual replacement. A number that ignores the whole-life cost is not defensible and will not survive an auditor.
Benefits with no owner and no measure. "Improved efficiency" is not a benefit anyone can be held to. Each claimed benefit needs a named owner, a baseline, a target, and a date. If no one will sign for it, leave it out.
Optimism instead of contingency. Single-point estimates with no range, built on last year's prices, were a common casualty in 2022. Estimates need a stated basis, a date, and a contingency that reflects real volatility — not a round 10 percent dropped in to look prudent.
No honest risk register. A case that lists only minor, easily-managed risks reads as naive. Name the risks that could actually kill the project, including labour and material availability, and show how each is mitigated or who carries it.
Assumptions buried or missing. Every number rests on assumptions about demand, prices, timing, or capacity. If those are not written down, no one can test them — and when one proves wrong, the whole case loses credibility at once.
Building one that holds
A durable business case is traceable. Every figure points to a source, every benefit to an owner, every assumption to a line someone can challenge. Write it so a reviewer who was not in the room can follow the logic from problem to recommendation without you sitting beside them.
State the problem and the strategic fit before any solution — what changes if nothing is done.
Show the options you considered and why the others lost, not just the one you chose.
Use whole-life costs with dated estimates, a clear basis, and contingency sized to the real risk.
Make benefits measurable, owned, and time-bound, then plan to track them after delivery.
Keep a candid risk register and a plain list of assumptions a reader can verify.
The test is simple: hand the case to a sharp colleague who knows nothing about the project. If they can find the weak number, you have found it before the board did. The point is not to make the project look certain — nothing is — but to make the thinking visible and honest enough that a reasonable approver can say yes and defend that yes later.
If you want a business case that holds up when a funder or auditor pushes on it, XNM's program & project delivery advisory can help you build and stress-test it before it goes forward.