Scenario Planning: Best Case, Base Case and Worst Case Forecasts

Published: 7 March 2026
Practical accounting guide

Good financial planning starts before a deadline or commitment becomes urgent. For owner-managed businesses and limited companies, building best-case, base-case and downside forecasts is easier to manage when current figures, upcoming obligations and the commercial reason for the decision are reviewed together. A short planning routine can turn a last-minute accounting question into a controlled business decision.

FocusBusiness Scenario Planning
Useful forOwner-managed businesses and limited companies
FromDD Accounting
Key takeaway

Review building best-case, base-case and downside forecasts while there is still time to change the timing, funding or structure of the decision. Current bookkeeping and realistic forecasts give the planning process something reliable to work from.

01

Start with current figures

Planning based on an old year-end figure can give a false sense of security. Bring the bookkeeping up to date and identify what has changed since the last accounts were prepared. For building best-case, base-case and downside forecasts, the most useful starting point is usually a current view of cash, profit, liabilities and committed spending rather than turnover on its own.

02

Identify the trigger point

The reason for reviewing the position matters. In this case the trigger is sales are uncertain or the business is considering a material commitment. Write down the decision that needs to be made, the date by which it needs to be made and the financial consequences if nothing changes. This keeps the accounting work focused on a real decision instead of producing figures with no clear purpose.

03

Bring the right information together

Useful planning normally needs more than one report. Relevant inputs can include current management figures, pipeline, recurring revenue, known cost changes, staffing plans and tax commitments. Looking at these together helps prevent a decision that solves one issue while creating another, such as improving reported profit while creating avoidable pressure on cash flow.

04

Make the decision and set a review date

Once the options are clear, record what has been decided and what assumption the decision relies on. agree in advance what action would be taken if performance moves towards the downside scenario. Set a date to revisit the position so the plan can be adjusted if sales, costs, staffing or tax estimates move away from expectations.

Practical checklist

What to do next

  • Bring bookkeeping up to date before planning
  • Define the decision and deadline clearly
  • Include cash, tax and committed costs
  • Compare more than one realistic option
  • Set a date to review the assumptions again
Relevant specialist support

Trade accountancy resources related to this topic

This topic is also relevant to the following specialist trade accountancy resources where the same accounting issue commonly arises.

Helpful answers

Frequently asked questions

Why is current bookkeeping important for planning?

Because decisions based on incomplete or old figures can miss recent costs, unpaid invoices, tax liabilities or changes in profitability.

Should planning only happen at year end?

No. Many useful decisions need to be considered during the year while there is still time to change timing, pricing, spending or funding.

What if the figures change after the plan is made?

That is normal. A useful plan is reviewed and updated as actual results become available rather than treated as a fixed prediction.

Need support?

Turn the figures into a clearer accounting process

DD Accounting can help with financial forecasting, management accounts, business planning and wider accountancy support.

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This article provides general information only and does not replace advice based on your individual circumstances. Tax rules and reporting requirements can change.

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