# Cash Flow Scenario Planning: Best, Expected and Worst Case

Source: https://www.cashflowforecasttemplates.co.uk/guides/cash-flow-scenario-planning-best-expected-and-worst-case
Updated: September 25, 2026

> Cash flow scenario planning means building several versions of your forecast, usually expected, best and worst case, by changing a few key assumptions such as sales, payment timing and costs. The worst case shows how much cash buffer or funding you need; the best case shows what growth would require. Decide your responses before you need them.

A single forecast gives you one answer to “how much cash will we have?”. But the future rarely follows the plan. **Scenario planning** builds a few alternative versions of the forecast, so you can see how cash holds up if things go better or worse, and decide in advance what you’d do. It’s one of the most useful habits a business can have, and it takes far less time than it sounds.

## The three standard scenarios

| Scenario | What it represents | Main question it answers |
|---|---|---|
| Expected | Your realistic plan | Where are we heading? |
| Worst case | A plausible bad year | How much buffer or funding do we need? |
| Best case | Faster growth than planned | Can we afford to grow this fast? |

## Choosing the assumptions

Change only a few assumptions, the ones that move cash most. For most businesses those are:

- **Sales volume**, up or down
- **Customer payment timing**, especially for your largest customers
- **Key costs**, such as materials, energy or wages
- **Timing of a major event**: a funding round, a big contract, a new location opening

### Typical worst case

- Sales 15 to 30 percent below expected
- The largest customer paying 30 to 60 days later
- Main costs 5 to 10 percent higher
- A key event delayed by two or three months

### Typical best case

- Sales 10 to 20 percent above expected
- Extra stock, staff or materials needed to deliver them, paid in advance
- Customer payment timing unchanged

The best case often shows something surprising: faster growth can make cash **tighter** in the short term, because costs to deliver the growth come before the extra receipts.

## Worked example

A small business has an expected forecast with a lowest balance of $12,150 in March, just below its $15,000 buffer. Its scenarios apply 80 percent of cash in and 105 percent of cash out for the worst case, and 110 percent in and 97 percent out for the best:

| | Expected | Worst case | Best case |
|---|---|---|---|
| Lowest balance | 12,150 | −105,000 | 29,000 |
| Months below buffer | 3 | 10 | 0 |
| Year-end balance | 23,450 | −105,000 | 81,000 |

The worst case isn’t a prediction; it’s a warning. Cash falls below the buffer by the second month and keeps falling all year, which means a 20 percent drop in receipts isn’t a timing problem this business could borrow through: it would need structural changes. The owner decides now which costs would be cut, and in what order, if sales run 10 percent below forecast for two consecutive months, and arranges a modest facility to cover the time those cuts take to work.

## Plan your responses in advance

The real value of scenario planning is deciding **what you would do** before you have to decide under pressure. For the worst case, write down:

- **Early warning signs**: sales two months below forecast, a key customer paying late, costs rising.
- **Actions and their triggers**: “If sales are 15 percent below forecast for two months, pause the planned hire and reduce marketing by a third.”
- **Funding options**: an agreed facility, owner funds, delaying capital spending.

For the best case, write down what you’d need: when to order extra stock, when to hire, and whether you’d need finance to fund the growth.

## How to build scenarios

The simplest method uses **multipliers**: a single cell for the percentage of expected cash in and cash out, applied to every line. It’s quick and easy to switch. Our premium templates do exactly this, with an expected, best and worst case switch on the Settings tab that flows through the weekly, monthly and 3-year views.

For more precision, change specific lines, such as the largest customer’s payment dates, rather than applying a blanket percentage. Keep the scenario changes clearly labelled so anyone can see what each version assumes.

## Reading the results

1. **Lowest balance in each scenario.** Is the worst case below zero? By how much?
2. **When it happens.** The timing tells you how long you have to act.
3. **How it recovers.** A dip that recovers is a timing problem; one that keeps falling is structural.
4. **The gap between expected and worst case.** That gap is roughly the buffer or facility you should have in place.

## Scenarios in different businesses

- **Seasonal businesses:** test a weak peak season, not just a weak average year. A 20 percent drop in December matters far more to a retailer than a 20 percent drop in February.
- **Project businesses:** test a large project slipping by two months, since that moves both receipts and costs.
- **Subscription businesses:** test churn one or two points higher, which compounds over the year.
- **Startups:** test the funding round arriving three to six months late.
- **Businesses with one large customer:** test that customer paying 60 days late, or leaving.

## Beyond three scenarios

Sometimes a specific risk deserves its own scenario: losing your largest customer, a key supplier doubling prices, a funding round slipping six months, or a new location opening late. Model the one or two risks that would hurt most, rather than dozens of combinations.

## Sharing scenarios

Lenders, investors and partners respond well to scenarios, because they show you’ve thought about risk. Present the expected case as the plan, the worst case with the actions you’d take, and the best case with what it would require. Keep it to one page: a small table of lowest balance and year-end balance for each scenario, and a sentence on each.

## Common mistakes

- **A worst case that’s too mild.** If it never shows a problem, it isn’t testing anything.
- **A worst case that’s apocalyptic.** Plan for plausible, not impossible.
- **Changing everything at once**, which makes it hard to see what matters.
- **Building scenarios and not acting on them.**
- **Forgetting that growth uses cash** in the best case.

## Tools


The free templates are single-scenario; premium [industry templates](/cash-flow-forecast-template) add the one-click scenario switch, plus actual vs forecast tracking so you can see which scenario reality is following. For the basics of building the forecast itself, see [how to make a cash flow forecast](/guides/how-to-make-a-cash-flow-forecast).

### What is cash flow scenario planning?
Creating alternative versions of your cash flow forecast with different assumptions, typically expected, best and worst case, to see how cash holds up under each.

### How pessimistic should a worst case be?
Plausible, not catastrophic. Common choices are sales 15 to 30 percent lower, the largest customer paying 30 to 60 days late, and costs 5 to 10 percent higher.

### Why do I need a best case?
Growth uses cash. A best case shows how much extra stock, staff or working capital faster growth would need, so success doesn’t cause a cash crunch.

### How many scenarios should I have?
Three is usually enough. More scenarios take longer to maintain and add little for most small businesses.

### How often should I update scenarios?
Whenever you update the main forecast, and whenever a major risk or opportunity changes.