Base, Upside, Downside: How to Think About Scenarios

Every forecast is a guess. The question is whether you're making one guess or three.

Most cash flow forecasts present a single view of the future — your best estimate. That's useful, but it's incomplete. A single forecast tells your board what you think will happen. It doesn't tell them what happens if you're wrong.

What scenarios actually are (and aren't)

Scenarios are not predictions. They're structured "what-if" exercises that help you understand the range of outcomes your business might face.

Base case — your best estimate. This reflects what you genuinely expect based on current contracts, historical patterns, and known commitments.

Upside case — what happens if things break your way. A large customer pays early, a new contract closes ahead of schedule, or operating expenses come in lighter. This should reflect realistic positive outcomes, not fantasy.

Downside case — what happens if things go sideways. A major customer delays payment, a project slips, an unexpected expense hits. This is the scenario your lender and board care about most.

Why your board wants three numbers

When you present a single-point forecast, you're implicitly claiming confidence in every assumption behind it. Three scenarios communicate something more valuable: you've thought about what could go wrong, you know your exposure, and you have a plan.

It shifts the conversation from "is this number right?" to "what are the triggers that move us between scenarios?" That's a far more productive discussion.

How to define your scenarios

The temptation is to set upside and downside as simple percentage adjustments. That works as a starting point, but the best scenario analysis is more targeted. Think about which specific line items have the most uncertainty and impact: collection timing on your largest customers, payroll cycles, debt service payments, tax installments, capital expenditure timing.

For each scenario, adjust only the variables that realistically move. Your rent doesn't change in a downside case. Your largest customer's payment timing might.

The mechanical side

In a well-built model, scenarios should work like a layer on top of your base case. Your input tabs always reflect your base case. The scenario engine applies adjustments, and a toggle switches the summary view. You maintain one set of inputs, not three.

Using scenarios in practice

Each week when you enter actuals, compare where you're tracking relative to your three scenarios. If actuals have trended toward the downside for three consecutive weeks, that's a signal to act.

Define trigger points in advance. If ending cash drops below a specific threshold in the downside case, what's your playbook? Having these decisions pre-made is the difference between managing cash and scrambling for it.