Scenario planning: building 3 financial cases (worst, base, best)

Quick answer. Financial scenario planning means building several trajectories (typically three: worst, base and best) rather than a single forecast. You vary a few critical variables, measure the impact on cash flow and profitability, then prepare action plans and trigger thresholds so you can react quickly when reality diverges.

Many business owners run their company on a single forecast, usually built on the assumption that suits them best. The problem is not optimism: it is the absence of a plan B the day revenue dips, a client pays at 90 days instead of 30, or a cost overruns. Scenario planning addresses that fragility. It does not aim to predict the future, but to prepare a response.

This article, written by Hayot Expertise (a chartered accountancy firm registered with the Ordre des experts-comptables of Île-de-France), sets out a concrete five-step method to build your three financial cases, identify the variables that really matter, and decide in advance when and how to act.

A single forecast gives a false sense of control. It sets a trajectory, but never tells you at what point the gap becomes dangerous. Yet uncertainty is the rule, not the exception: a lengthening payment term, a postponed order or a supplier price increase are enough to drain cash.

Building multiple forecasts changes the nature of the exercise. You no longer think in terms of "how much will I earn", but in terms of "what happens if". This is exactly what a banker or investor looks for in a file: they want to see the downside case and your ability to hold it.

Common case: the optimistic forecast that breaks#

In start-up and early-growth files, the most frequent sticking point is the same: an owner builds the business plan on a high revenue assumption, with clients expected to pay on the spot. Six months later, volume is fine but payments arrive at 60 days. The accounting result stays positive, yet cash is dry. The company is profitable on paper and in difficulty in reality. A costed worst-case scenario would have revealed that cash gap before it happened, leaving time to arrange a solution.

This is the method we apply in pilotage files. It works as well for a new business as for an established company that wants to secure an uncertain year.

1. Identify the key variables. List the parameters that truly drive your result and cash flow: revenue (volume and price), margin rate, fixed and variable costs, client payment terms, and working capital requirement (WCR). Keep only those with a material effect.
2. Build the realistic base scenario. This is your most likely trajectory, based on reliable data: history, order book, prudent but credible assumptions. This case serves as a benchmark, not a marketing target.
3. Define the worst-case and best-case assumptions. Vary one to three critical variables, not all at once. The worst case must remain plausible and costed (for example lower revenue and slower client payments), while the best case stays realistic (a successful ramp-up without cost overruns).
4. Calculate the impact on cash flow and profitability. Translate each scenario into a forecast income statement and, above all, a monthly cash-flow plan. It is the cash-flow plan that reveals the low point and the moment the situation tightens.
5. Prepare action plans and trigger thresholds. For each case, decide in advance which action to launch and at what threshold: cut certain costs, draw on a credit line, postpone an investment, step up collection. A scenario only has value if it leads to a prepared decision.

For the mechanics of the figures, it helps to rely on a solid framework: our team can help you build a costed forecast consistent across the three cases, starting from reliable management data.

The table below illustrates, for teaching purposes, how three scenarios play out on the same variables. The values are examples meant to show the mechanism, not figures to reuse as such.

What stands out in this example: between the base case and the worst case, it is not only the revenue drop that weighs, but the longer client payment term combined with the higher working capital requirement. Two cash-flow variables can do more damage than a simple drop in activity.

Our reading#

The natural reflex is to vary revenue and stop there. That is a mistake. In most files, the variables that tip cash flow are the client payment term and the working capital requirement. A company can post a good result and still run short of cash because it is financing its clients' growth. The most instructive worst-case scenario is rarely a general recession: it is the one where activity holds but collections slow down.

These two notions are often confused. Yet they answer different questions.

• Sensitivity analysis varies a single variable, all else being equal, to measure its isolated impact. Example: what happens to my cash flow if the client payment term moves from 45 to 60 days, everything else unchanged? It ranks the variables and identifies those that deserve the most attention.
• Stress testing tests an extreme but plausible shock: the loss of a client representing a large share of revenue, a sudden rise in raw-material prices, a financing delay. The aim is not average realism, but resilience in the worst credible case.

Sensitivity analysis tells you where you are fragile; the stress test tells you whether you can take the hit. Both feed the construction of the worst-case scenario.

The underestimated risk#

The danger is not getting the forecast wrong: it is discovering the critical threshold too late. Many companies know their cash can tighten, but no one has written down at what exact level to act, or who decides. As a result, they react in a rush, at the very moment when room for manoeuvre is thinnest and negotiating a credit line is hardest. Setting thresholds in calm conditions buys time to negotiate from a position of strength.

A scenario stays theoretical until it translates into action rules. The following table links each critical variable to its impact and to the prepared response, with a trigger threshold.

In practice#

In concrete terms, a useful scenario-planning setup takes little: a spreadsheet or tool with three columns (worst, base, best), a monthly cash-flow plan per case, a list of costed thresholds, and a regular review. To stay reliable, it all has to rest on up-to-date figures: that is the whole point of making your management data reliable beforehand. You can also test the effect of working capital on your liquidity with our WCR simulator before building your cases.

The classic forecast answers the question "what is my most likely trajectory". Scenario planning answers "how do I react if it does not happen". The first produces a figure; the second produces a decision grid.

That does not mean the two are opposed. The base scenario is precisely a classic forecast. Scenario planning enriches it by framing it with two variants and attaching action plans. To go further on operational monitoring, see how to manage cash flow day to day and how to calculate the break-even point, which is an essential marker of the worst case. All of this fits into a broader approach to financial management of the company.

Points to watch#

• A doom-laden worst case is useless: too dark, it lacks credibility and triggers no action. It must stay plausible and costed.
• Varying every variable at once blurs the reading. Isolate one to three critical variables per scenario.
• A frozen scenario becomes wrong over time. It must be revised whenever the context changes: a new major client, a lasting cost increase, shifting payment terms.
• Without written trigger thresholds, the exercise stays decorative. The value lies in the prepared decision, not in the table.

To anchor these scenarios in accounting reality, it helps to know how to analyse a balance sheet so you start from a reliable financial snapshot.