How to Build a Business Case Model your Buyer Can Defend.
You have a champion who believes in the deal but needs to take a number to finance or a senior leader who will stress-test it.
A business case is not just math. It is the story your champion tells when you are not in the room. If the model is complicated, opaque, or full of vendor-supplied assumptions, finance will pull it apart and the deal stalls. A simple, transparent model built from the buyer's own numbers is much harder to dismiss - because the buyer already owns it.
Where it goes wrong
Deals that reach late stage and then go quiet. The champion liked the idea but could not defend the numbers upstairs. You lose not to a competitor but to 'we need more time to validate the ROI'.
What you'll be able to do
The AE can build a one or two slide model with the buyer that shows value clearly, uses conservative assumptions the buyer agreed to, and gives finance something they can actually approve.
How to do it
Pick one or two primary value drivers - revenue
Pick one or two primary value drivers - revenue gained, cost removed, or risk reduced. Do not try to quantify everything. Three to five inputs on a visible assumptions section is enough.
Use the buyer's own baselines
Use the buyer's own baselines. In discovery, ask for volumes, current performance rates, and resource costs. Their numbers beat any benchmark you bring.
Co-create the improvement assumption
Co-create the improvement assumption. Say: 'Customers in a similar position tend to see 10 to 20 percent improvement here. What would feel credible to model - maybe 5 percent to stay conservative?' Let them pick the number.
Show three cases - conservative, expected, and best -
Show three cases - conservative, expected, and best - so finance sees you have not just picked the flattering scenario.
Calculate annual value, total cost of ownership, ROI percentage,
Calculate annual value, total cost of ownership, ROI percentage, and payback period. Finance thinks in these terms. Keep the formula visible: impact equals baseline times improvement percentage times monetary value.
Put assumptions on the slide itself, not buried in
Put assumptions on the slide itself, not buried in a spreadsheet. If finance can see the inputs, they can adjust them rather than reject the whole model.
See the difference
The AE sends a PDF from the vendor ROI calculator showing '312% ROI and 4-month payback' with no explanation of inputs. The champion forwards it. Finance asks where the numbers came from. Nobody knows. The deal goes to 'pending further review'.
The AE runs a 20-minute working session with the champion. Together they agree: 8 sales reps, average deal size of $40k, current win rate 22%, target improvement 3 percentage points (conservative). That is roughly $96k additional revenue per year against a $28k annual cost - payback under four months. The AE puts those five inputs on a single slide with a note: 'Assumptions agreed with [champion name] on [date].' Finance can see exactly where the number came from and adjust if they want to.
The AE can build a one or two slide model with the buyer that shows value clearly, uses conservative assumptions the buyer agreed to, and gives finance somethin
How you'll know it's working
You have got it when your champion can walk a finance reviewer through the assumptions in under two minutes without calling you.
Questions people ask
How do you build a business case model your buyer can defend?
A business case is not just math. It is the story your champion tells when you are not in the room. The AE can build a one or two slide model with the buyer that shows value clearly, uses conservative assumptions the buyer agreed to, and gives finance something they can actually
What is the most common mistake to avoid?
Deals that reach late stage and then go quiet. The champion liked the idea but could not defend the numbers upstairs.
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