Profit and cash are not the same thing. A business can show sales on paper while still struggling to pay a supplier, rent or tax bill when money arrives later than expected. This practical Fapeza guide shows how to create a small-business cash flow forecast for a UK sole trader or microbusiness.
A forecast is a planning tool, not a promise. Keep it realistic, update it regularly and get accountant or adviser input where your situation is complex.
What is a cash flow forecast?
A cash flow forecast estimates when money will enter and leave your business. It normally starts with the bank balance you have today, adds expected inflows, subtracts expected outflows and shows the projected closing balance for each week or month.
That is different from a profit forecast. Profit focuses on revenue minus costs, while cash flow focuses on timing. An invoice may count as a sale before the customer pays. A yearly insurance payment may leave the bank in one month even though it supports the business for longer.
Why a 13-week forecast is useful
A rolling 13-week forecast gives a small business enough visibility to see upcoming pressure without pretending that every number twelve months from now is certain. It is especially useful when income varies, customers pay on different terms or costs rise during particular seasons.
Start with weekly columns. Once the process is working, create a broader monthly view for annual expenses, tax planning and investment decisions. The best forecast is one you will actually update.
Build the forecast in six steps
- Enter the opening balance. Use the amount genuinely available for business payments, not money you expect but have not received.
- List expected inflows by date. Include confirmed customer payments, subscriptions, refunds and other income. Mark uncertain invoices separately.
- List fixed outflows. Add rent, software, insurance, wages, finance payments and regular subscriptions on their actual payment dates.
- Add variable costs. Estimate materials, delivery, advertising, travel, transaction fees and professional support. Use a cautious figure when the amount is uncertain.
- Reserve for tax and annual bills. Put future tax, accounting, renewals and equipment replacement into the forecast before the money is spent elsewhere.
- Review the closing balance. If a week goes negative, work out the cause early. You may need to move a purchase, invoice sooner, negotiate terms or reduce discretionary spending.
Simple forecast structure
| Line | Week 1 | Week 2 | Week 3 |
|---|---|---|---|
| Opening balance | £2,000 | £1,500 | £2,100 |
| Customer payments | £900 | £1,300 | £700 |
| Regular costs | −£650 | −£700 | −£650 |
| One-off cost | −£750 | £0 | −£200 |
| Projected closing balance | £1,500 | £2,100 | £1,950 |
The figures above are only an example of layout. Replace them with your own payment dates, costs and tax assumptions. A forecast should show the reasoning behind each number so that you can change one assumption without rebuilding the whole document.
Ways to improve cash timing
- Send a clear invoice as soon as the work or milestone is complete.
- State payment terms, accepted payment methods and late-payment process in writing.
- Ask new customers about their procurement timetable before accepting a large project.
- Review subscriptions every quarter and cancel tools that are not being used.
- Keep a short list of costs that can be delayed without harming delivery.
- Do not use a forecast to justify spending money you do not yet have.
For record-keeping basics, refer to the GOV.UK guidance for self-employed records. If you are choosing an account for business payments, see this UK business-account guide.
Common forecasting mistakes
The most common mistake is treating every sales lead as guaranteed income. Use separate rows for confirmed, probable and uncertain receipts. Another mistake is forgetting VAT, tax, annual renewals, refunds, equipment replacement or quiet periods. Finally, do not update the forecast only when there is a crisis. A fifteen-minute weekly review is more useful than a large emergency spreadsheet.
Cash flow forecast FAQ
How often should I update it?
Weekly is a good starting point for a small business with changing income. A monthly review may be sufficient for a stable service business, but update it whenever a major invoice or cost changes.
Should tax be included?
Yes. Include a planned reserve based on your situation, but do not treat a generic percentage as personal tax advice. Confirm the amount and deadlines with HMRC or a qualified adviser.
What if the forecast turns negative?
Investigate the exact week and cause first. Then consider earlier invoicing, a revised payment schedule, postponing non-essential spending or asking for professional advice before taking on new debt.
Use best-case, base-case and cautious scenarios
A single forecast can create false confidence. Create three versions: a base case using the payments you reasonably expect, a cautious case where some customers pay late, and a stronger case where confirmed work arrives on time. Keep the cautious case realistic rather than making every number extreme. The purpose is to see which decisions remain safe under different conditions.
For each scenario, mark the point at which you would act. That might mean delaying a non-essential purchase, contacting a customer about an invoice, reducing a subscription or asking an adviser for help. Decide these actions before a cash shortage becomes stressful.
Questions for your weekly review
- Which expected payments are now overdue or less certain?
- Have any supplier, delivery or software costs changed?
- Are upcoming tax, insurance or renewal payments included?
- Which invoices can be sent, corrected or followed up today?
- Does the closing balance still support the next two weeks of commitments?
Keep notes beside the forecast so you remember why an amount changed. Over time, compare your estimates with what actually happened. That simple review makes the next forecast more accurate and exposes recurring seasonal patterns.