How to Build a Financial Forecast for a Small Business
A financial forecast is an estimate of your future income, costs and cash, built from your past results and clear assumptions about what happens next. To build one, gather clean records, set assumptions, project sales and costs, turn them into cash, and compare against reality each month.
What is a financial forecast?
It is a set of projected numbers for a future period, usually a year, built from what you know today. A typical small business forecast has three parts that tie together:
- Profit and loss forecast: expected sales and costs, giving expected profit.
- Cash flow forecast: when money is expected to come in and go out.
- Balance sheet forecast: what you expect to own and owe at the end of each period.
A forecast is an estimate, not a commitment. It is your current view of the most likely outcome, and it is updated as facts change. Do not confuse it with a budget: a budget is a target you set, while a forecast is what you now expect to happen. Our budget vs actual guide covers how the two are compared.
Why build a financial forecast?
- To see whether cash will run short before it does.
- To test decisions such as a hire, a price change or an equipment purchase.
- To give a lender or investor numbers they can ask questions about.
- To spot which assumptions matter most.
How do I build a financial forecast step by step?
- Start with clean history. Your last year or so of actuals, by month, from reconciled books. If records are behind, fix that first. See our bookkeeping and catch-up bookkeeping pages.
- Choose the period and detail. One year by month suits many small businesses. Add a weekly view when cash is tight.
- Write down assumptions. Sales growth, prices, number of staff, payment terms, major known costs. Keep them in one visible place so they can be changed.
- Forecast sales. Use known contracts, repeat customers and your realistic pipeline. Do not use hope.
- Forecast costs. Fixed costs (rent, salaries) are the easiest. Variable costs usually move with sales.
- Calculate profit. Sales minus costs for each month.
- Convert to cash. Adjust for when customers actually pay, when you pay suppliers, and for loan repayments, equipment purchases and owner draws. This is the cash flow forecast.
- Check the balance sheet. It should balance. If it does not, something is missing.
- Test scenarios. Make a cautious case and a poor case. See what is scenario analysis.
- Compare monthly and update.
Cash flow forecast format
If you only build one part, build cash. A simple format has opening cash, cash in, cash out and closing cash for each period. The cash flow forecast template page lays this out, and the thirteen-week cash flow forecast page shows the weekly version.
A simple worked example
The numbers below are invented to show the logic.
Example (illustrative numbers only):
| Assumption | Value |
|---|---|
| Last year's monthly sales | $40,000 |
| Expected growth next year | 5% |
| Monthly costs that stay fixed | $22,000 |
| Variable costs as a share of sales | 30% |
Forecast monthly sales: $40,000 x 1.05 = $42,000. Variable costs: $42,000 x 30% = $12,600. Forecast monthly profit: $42,000 minus $22,000 minus $12,600 = $7,400.
If customers pay on average a month after the sale, the cash you see in the bank in a given month reflects last month's sales, not this month's. That gap is why the profit forecast alone is not enough.
What are the common mistakes?
- Starting with a target and working backwards. That produces a wish list, not a forecast.
- Counting sales before they are likely. Include signed work and repeat customers first, and treat the rest with care.
- Forgetting the timing of cash. Profit and cash arrive at different times.
- Leaving out one-off items. Equipment, deposits, loan repayments and annual bills all hit cash.
- Never comparing to actuals. The comparison is where you learn.
How accurate should a forecast be?
Not exact. It should be useful and honest. A forecast that is wrong by a known margin and updated often beats a precise one made once a year. Track the difference between forecast and actual and ask why.
When a financial forecast is not worth the effort
- The business is too young to have any history and sales are very uncertain. A short cash view may be all you can defend.
- Nobody will update it. A stale forecast is worse than none.
- The records behind it are unreliable.
- You only need a thirteen-week cash view, not a full model.
Who can build it with me?
Our fractional CFO service includes forecasting and cash flow planning, scenario planning and budget development. See what we do. For the broader context, read how to manage cash flow in a small business.
English Oak Financial does not prepare tax returns, audit accounts or give investment advice. This page is general information, not tax or investment advice.
What English Oak Financial charges
English Oak Financial starts the fractional CFO from $2,500 a month. Pricing is custom to your business and charged as one fixed monthly fee that includes all the work required. See pricing.
Need this done for you? See our Fractional CFO & Advisory service, or pricing. English Oak Financial does not prepare tax returns, perform audits or give investment advice. This guide is general information, not tax, legal or investment advice.
Related pages
Common questions
What is a financial forecast?
It is an estimate of future income, costs and cash, based on past results and stated assumptions. It is updated as facts change.
What is the difference between a forecast and a budget?
A budget is a plan or target. A forecast is your current estimate of what will happen. Businesses compare the two to see where they are off course.
How far ahead should a small business forecast?
One year by month is common. Add a thirteen-week view when cash is tight. Beyond a year, the numbers usually become less reliable.
What do I need before I start a financial forecast?
Up-to-date, reconciled books for at least the last several months, a list of known commitments, and written assumptions.
Can I build a financial forecast in a spreadsheet?
Yes. A spreadsheet is a common choice. Keep assumptions in one place, use formulas for totals, and keep the layout simple enough that you can explain it.
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