# Confidence _Express uncertainty instead of hiding it._ --- You're asked to sign off a business case. The slide shows a 3x payback over 2 years on a proposed product launch. Upfront development cost of £500k followed by £1.5m of sales over next 18 months. Should you believe? --- You check the assumptions. The cost estimate assumes 6 months of development - but could be 4, could be 12. The £1.5m assumes 50 sales at book price of £30k each (no discounting) and 3 sales per month from day one. Assume dev takes 9 months instead of 6 - cost rises to £750k and you've lost a quarter of your selling window. And the first ten customers need discounting to close, so average price is closer to £25k. Sales come in at 2 per month instead of 3. You're looking at 30 sales at £25k - £750k of revenue against £750k of cost. None of these assumptions is pessimistic. Each is a plausible downside of an uncertain input. But stack the three and the payback disappears. The slide says 3x return. The honest range is probably somewhere between breakeven and 2x. --- Not all assumptions matter equally. Price discounting costs you perhaps £150k across early deals. Worth watching but not fatal. But a development delay moves everything at once. It doesn't just add direct cost, it takes months off your selling window. And the revenue you do collect arrives later, which matters if you're funding the project from cash. Most forecasts have this shape. Multiple inputs in the spreadsheet, but one or two where being wrong cascades through the whole model. --- Instead of "3x return over 2 years," the slide should say "between 1x and 3x, depending mainly on how long development actually takes." The conversation changes from "approve or reject" to "what would we need to see by month three to know whether we're on track?" If development is on schedule at the midpoint, the rest of the model holds. If it's slipping, you know early enough to adjust before the full impact lands. You'll never remove the uncertainty. You can stop pretending it isn't there. ---