Every failed project has a backstory—and often, it starts with a business case built on shaky assumptions. Learn the five most common flaws that sabotage investment, derail execution and erode value.
A strong business case doesn’t ensure success but gives your project a fighting chance. On the other hand, a flawed business case can kill a project before it even begins.
Too often, business cases come riddled with flaws, even some so fatal that no amount of expert project management or sponsorship can overcome the damage. If the foundation is shaky, the entire structure collapses.
These mistakes are common and can bring disastrous consequences. Here’s what they are – and how to steer clear.
Flaw #1: Blind optimism – Unrealistic benefits and assumptions
The road to project failure is paved with overly ambitious assumptions and wishful thinking. Many business cases promise sweeping benefits without fully accounting for execution challenges, hidden costs, or the behavioural shifts needed to make those benefits real.
What seems like a sure return on investment can unravel the moment reality sets in.
How to avoid it: Be ruthless with assumptions. Test projections against real-world data, challenge rosy estimates and factor in potential obstacles. A strong business case doesn’t just sell a dream – it prepares for the tough work required to achieve it.
ROI isn’t just about dollars and cents. Consider qualitative benefits like customer satisfaction and regulatory compliance. Using an ROI narrative can build a case that blends financial logic with strategic vision.
Flaw #2: The leadership black hole – Lack of alignment and stakeholder engagement
Even the best-structured business case will fail if key decision-makers aren’t on board. Without leadership backing, momentum fades as projects are deprioritised or deprived of resources as a result of less internal focus.
Sometimes, resistance is obvious. Other times, it’s subtle – leaders may nod in agreement but never fully commit. Either way, a business case without true alignment is a project with unmitigated risk that will erode outcomes and benefits.
How to avoid it: A strong business case builds buy-in. Engage leadership early, making sure to address their concerns. Ensure key departments (like IT, finance and operations) are part of the conversation from the outset. Silent resistance can sink a project just as easily as vocal opposition.
Flaw #3: Wishful budgeting – Cost estimates without enough wiggle room
Nothing derails a project faster than an underestimated budget. Decisions often get made based on dollars, not purpose, so items are descoped or work is either rushed or delivered with inferior quality – all so we don’t have to ask for more funding.
Yet, many business cases present cost estimates as if they’re set in stone, ignoring the reality that they are in fact estimates – subject to variance and impact from risks, internal delays and even external factors.
The outcome of this flaw? A business case that looks responsible on paper, but quickly falls apart when the numbers don’t hold up. Ultimately, this can lead to ROI challenges (costs go up, but benefits are the same).
How to avoid it: CFOs won’t like this, but embrace financial uncertainty – responsibly. Instead of rigid cost estimates, use confidence ranges that reflect the project’s true complexity. Quantify how much additional cost would you bear to pursue this benefit – does the risk outweigh the reward?
Finally, build in contingency funds and account for external risks. A business case grounded in financial reality stands a far better chance of delivering on its promises than one that hopes for the best.
Flaw #4: Scope amnesia – Undefined or missing scope
One of the quickest ways to burn through a budget is to leave critical scope elements undefined. A poorly defined business case invites inclusions, and inclusions invite costs and complexity – which frequently leads to disaster. Also, teams may interpret scope differently, leading to costly rework, shifting priorities and unnecessary complexity.
How to avoid it: Be crystal clear on what’s in and what’s out. Anticipate areas where scope may shift and establish a framework for managing changes. A well-structured scope reduces confusion and the likelihood of costly surprises.
Flaw #5: The crystal ball syndrome – Business cases that plan too far ahead
This may seem counterintuitive to Flaw 4, however there is an important difference. Scope amnesia (undefined or missing scope) is about the clarity of vision, while crystal ball syndrome (planning too far ahead) is about the ambition of the vision.
If you’re a little confused, allow us to explain. Many business cases try to predict the future in painstaking detail, laying out multi-year plans as if market conditions and business priorities will remain unchanged (spoiler: they won’t). But the longer the timeline, the more fragile the plan. A business case that assumes today’s reality will hold for years to come is already outdated as soon as it’s committed to paper.
How to avoid it: Instead of committing to a rigid long-term strategy, business cases should be structured into shorter, adaptable phases. That’s not to say you shouldn’t embark on multi-year transformations; on the contrary, some changes will always take longer to achieve. However, breaking the overarching business case into support initiatives in 6- to 12-month cycles allows organisations to reassess and make adjustments based on real-world developments.
A business case isn’t meant to be a “set and forget” document. It should be revisited throughout the project to ensure decisions stay aligned with its original intent and evolving business needs. Otherwise, it risks becoming just another forgotten file on the shelf.
A business case is more than just an approval form
Yes, a business case’s first job is to secure approval – but that’s just the start. A truly effective business case isn’t just a justification for funding; it’s laying the foundation for project success. If it’s built on blind optimism, weak alignment, or unrealistic assumptions, even the best execution won’t save it.
Before signing off on your next business case, take a hard look at its foundations. Are the benefits realistic? Is leadership truly aligned? Have costs been estimated with enough flexibility? Is the scope clear? And is the plan adaptable enough to survive the inevitable shifts in the business landscape?
A business case should be a roadmap, not a wish list. Get it right from the start, and you’ll set up your project to deliver real, lasting impact.
Quay Consulting is a professional services business specialising in the project landscape, transforming strategy into fit-for-purpose delivery. Meet our team or reach out to have a discussion today.
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