A business case for a purchase is the internal document that asks a company to spend the money. Someone inside the buyer’s company writes it, usually your champion, and it goes to people who may never see your pitch. It answers a bigger question than your proposal does. Your proposal says why you. The business case says why spend this at all, and why now.
It’s easy to leave that document to chance. We’d offer to draft it. Selling to a CFO covers the finance page inside your own proposal, and this post covers the document your buyer sends under their own name.
What happens after your champion says yes
Your champion likes you. Now she has to ask for the money. She opens her company’s template or a blank page, usually between other work, and tries to turn your proposal into something that sounds like her company wrote it. She may not have your numbers to hand. She may not know how to explain your implementation cost, or how to compare you fairly with the other option on her list.
A weak document often gets a request for more information. Then the next meeting comes and goes, and the deal drifts into no decision. You’ll probably never read the page that did it.
What goes in a business case for a purchase
The clearest framework we’ve found comes from government. HM Treasury’s guidance sets out the Five Case Model, the standard framework for business cases in the UK and Welsh governments, and it looks at every proposal from five angles. It was written for public projects, and the five angles fit any large purchase. Here’s how we’d translate them for a company buying from you.
| The angle | What the approver wants to know | What you can give your champion |
|---|---|---|
| Strategic | Why do we need this, and why now? | The problem in their words, their numbers and what happens if things stay as they are |
| Economic | Which option is the best value? | A fair comparison of the realistic options, including staying put |
| Commercial | Who carries which risk, and how do we pay? | Payment terms, contract length, service levels and the way out |
| Financial | Can we afford it, and whose budget pays? | Total cost by year, split into one-time and recurring |
| Management | Can we make this work? | The timeline, owners on both sides, the main risks and how success gets measured |
Three points in that guidance are worth borrowing.
- Carrying on has a cost. It warns against assuming an organization will do nothing if the proposal doesn’t go ahead, since business as usual still has costs, benefits and risks. Your toughest competitor is often the current way of working, so price it properly.
- The effort should match the decision. It says the work should scale with size, cost, complexity and risk. A modest purchase can get by on one page. A multi-year commitment may need all five angles written out.
- Assume you’re too hopeful. It lists optimism bias and sensitivity analysis as part of the economic case. In plain terms, expect your estimate to run high, then show what happens when the numbers move.
What to hand your champion
Start with three questions. Does your company have a template for this? Who approves a purchase this size? When’s the next meeting where it can get approved? The answers give you the format, the reader and the date.
Then send a draft built to be taken over.
- Put the ask at the top. How much, for what, from which budget, by what date and signed by whom.
- Write it in their voice. “We” means the buyer here. Your company appears as one of the options.
- Leave your logo off. It should read like an internal memo, because that’s what it’s going to be.
- Send something editable. A plain document she can paste into a template. A locked PDF makes her retype it.
- Lay out the options fairly. Include staying put, a cheaper fix and you. An approver will ask what else was considered, and she needs an answer that holds up.
- Use only numbers she gave you or approved. Mark internal costs, staff time and anything else you can’t know as blanks for her to fill. A blank beats a guess.
She’s going to rewrite parts of it. That’s the point, because by the end it’s hers.
Let the approver argue with the numbers
Approvers have been sold savings before. Our Waymark concept, a fleet telematics proposal for a coach operator, takes that head on. One Tuesday run in the proposal saves 13 percent of its fuel, and every other figure on the page uses 7. The finance director gets sliders for the diesel price and the savings rate, and he can watch the month when savings pass everything spent. As the note on that page says, a finance director who sets the assumption himself stops auditing ours.
The same logic works in a business case. State each assumption, show a conservative case beside the expected one, and make the inputs easy to change. Our free ROI calculator builds payback, return and a conservative case from the buyer’s own costs and benefits, on one page your champion can work from. If her finance team already trusts a spreadsheet of its own, use theirs.
Write the part that fits in a board pack
A big purchase can end up as a few lines in someone else’s meeting papers. Write those lines before anyone asks. Our Thornbury concept, a design-build proposal for four residence halls, gives the trustees five sentences, because that’s what fits on one page of a board pack. They cover what gets built, the most it can cost, when it’s ready, what happens if a bed isn’t ready, and how the buyer can stop after the first two halls.
Give your champion the same thing, five plain sentences she can drop into the papers as written. Our post on what makes a board presentation get a yes goes further if the deal reaches that room.
How it plays out
Say a director of operations wants to replace the scheduling system across her regions. She has a strong proposal in hand and a leadership meeting on Friday. Left alone, she’d spend the week’s evenings turning a sales document into an internal one.
Instead, the seller asks the three questions on Tuesday and sends a two-page draft that afternoon. The ask is at the top. Three options follow, staying on the current system, patching it with a cheaper tool, or switching. Costs run by year. The savings use the overtime figures she shared in discovery, with a conservative case beside the expected one. Her internal costs are marked as blanks.
She fills those in, changes whatever doesn’t sound like her company and sends it under her own name. The seller’s name appears once, in the options.
Questions we hear about business cases
Who should write the business case?
Someone inside the buyer’s company, because their name goes on it. The seller can draft it, and should offer to. A recommendation from a colleague carries weight that a vendor’s document can’t.
Won’t offering to draft it seem pushy?
Offer it as a time saver and it won’t. Try something like “If it helps, we can send a first draft you can rewrite.” If she says no, drop it and send her the raw numbers.
How is a business case different from an ROI calculation?
The return is one line of it. A business case also covers why now, what else was considered, who carries which risk, whose budget pays and who makes it work. A strong return with no owner can still get sent back.
What if the purchase goes through a formal RFP?
Then the case may come in stages, and your response feeds the last one. HM Treasury’s process ends with a full business case written during procurement, which has to explain why the shortlisted suppliers were chosen and why others were rejected. Even outside government, assume someone will have to explain why they picked you, and make that sentence easy to write.
Should the business case name our competitors?
That’s the buyer’s call. Give your champion a fair description of each type of option, and let her add the names. She knows what she can say internally, and you don’t want to be the one who got a rival’s numbers wrong.
The short version
A business case for a purchase is your buyer’s document, and your deal depends on it. It has to say why now, which option, who carries the risk, who pays and who makes it work. Offer a draft your champion can rewrite, with the ask at the top, the options laid out fairly, her numbers and a conservative case.
A good proposal makes that draft far easier to write, because the raw material is already there. That’s why we write our custom sales proposals around how the buyer decides, with an ROI or savings calculator as an add-on when the deal calls for it. For everyone else who weighs in, see writing for a B2B buying committee. If you’ve got a big deal where someone inside will have to ask for the money, start a proposal.
