Make the assumptions behind your plan reviewable

Keep the objective separate from the expectation

A budget sets out the income and spending the business intends to achieve. A forecast reflects the latest expectation using current information. Keeping both views available lets management assess progress towards its plan without hiding changes in the outlook.

Before adjusting a model, identify the operating decision it supports. Hiring, equipment purchases and new service capacity each depend on different assumptions. A useful plan makes those dependencies visible enough for someone other than its author to question them.

Build an assumption register alongside the model

Translate the operating plan into a limited set of drivers. For a project-based service business, these might include project start dates, delivery capacity, fee arrangements, billing milestones and collection timing. Separate commitments supported by agreements from estimates based on operating experience.

Record the evidence and its date. An old estimate can look authoritative after it has been copied through several planning cycles. When evidence is limited, state the gap and assign someone to resolve it. The illustrative register below gives a review meeting a practical starting point.

Assumption

the business activity, cost or timing driver being modelled.

Evidence

source, date, owner and any limitation that affects its use.

Dependency

the other assumptions or commitments affected if it changes.

Review trigger

an observable event that requires the assumption to be reconsidered.

Response

who will assess the event and which decision may need to change.

Create scenarios with a coherent operating story

Start with the current working expectation. Then examine a plausible alternative that matters to the decision, such as delayed project starts or slower collections. A further scenario could consider what the business would need if work arrived earlier than expected. These are conditions to explore, not predictions or assigned probabilities.

Change related inputs together. If a project starts later, consider the effect on delivery costs, billing milestones, staff availability and collection dates. Moving revenue alone can leave a scenario internally inconsistent. Review cash and operating performance together: a profitable plan may still require resources before customers pay.

Keep the scenarios understandable. Explain what changes, why the change is plausible and which management choice it tests. ICAEW's scenario guidance emphasises reliable data, relevance and plausibility; the purpose is to improve preparedness for different conditions.

Agree when management should act

For each scenario, identify the evidence that would prompt a review. Examples include a confirmed delay in a billing milestone, a material change in a supplier commitment or a shift in available delivery capacity. A trigger should be observable and linked to a decision, rather than a vague instruction to monitor conditions.

Discuss feasible responses before the event occurs. Which commitment can be revisited? What information must be obtained first? Who has authority to decide? Record the limits as well as the options so the plan does not assume that every response will be available immediately.

Use actual results to improve the next version

Compare results with the plan at an agreed interval. Distinguish timing differences from lasting changes in activity, then update the forecast using new evidence. Retain a short change log explaining important revisions and the decisions they affect. This turns planning into a reviewable management process while keeping uncertainty visible.