Cash flow forecast for small business UK

Running out of cash is one of the main reasons small businesses fail. A cash flow forecast helps you see when money is coming in and when it is going out, so you can plan ahead and avoid surprises. This article explains how to build and use a cash flow forecast for a small business in the UK, and what to include so it stays useful.

We cover why cash flow forecasting matters, what a simple forecast looks like, and how often to update it. This is for founders and SME owners who want to stay on top of their cash without turning into full-time finance managers.

Why small businesses need a cash flow forecast

Profit and cash are not the same. You can be profitable on paper and still run out of money if customers pay late, you pay bills and tax before cash arrives, or you invest in stock or equipment. A cash flow forecast shows your expected bank balance week by week or month by month so you can spot shortfalls early.

What it gives you

• Early warning of pinch points (e.g. a VAT or tax payment that coincides with slow receipts).
• A basis for talking to your bank or investors if you need funding.
• Clearer decisions on when to hire, spend, or hold back.

For more on how we do this with clients, see our Management Reporting and support for cash flow planning.

What to include in a simple cash flow forecast

A practical forecast usually covers the next 13 weeks (quarter) or 12 months. It lists:

Cash in

• Expected receipts from sales (when you actually get paid, not when you invoice).
• Other income (e.g. grants, refunds, loans).

Cash out

• Payroll (including PAYE and NI).
• Rent, utilities, and regular overheads.
• Supplier payments.
• VAT (if applicable).
• Corporation tax, and other tax payments.
• Loan repayments.
• One-off or irregular items (e.g. equipment, professional fees).

Opening and closing balance

Start with your actual bank balance (and any overdraft). Each week or month, add cash in and subtract cash out to get the closing balance. That closing balance becomes the next period’s opening balance.

Example

A small agency has £20,000 in the bank. It expects £30,000 in receipts over the next four weeks and £25,000 in payments (payroll, rent, suppliers, VAT). So closing balance in four weeks is £25,000. The following month it has a large corporation tax payment; the forecast shows a dip. They can plan to delay a non-essential cost or arrange a short-term facility. HMRC guidance on managing cash flow is a useful external resource.

How often to update your cash flow forecast

A 13-week rolling forecast is often enough: each week or fortnight you add a new week at the end and update the rest with latest actuals and assumptions. That keeps the forecast relevant without taking too much time. Some businesses do a monthly forecast for the full year; others focus on the next quarter in detail. The right frequency depends on how volatile your cash is and how much time you can give it.

Who can help build and maintain it

You can do a simple forecast in a spreadsheet. Your accountant or a fractional CFO can build a more robust model and help you interpret it. At Figures Chartered Accountants we produce rolling cash forecasts for clients so they always know where they stand. We flag pinch points early and tie the forecast to your actual bank and accounting data where possible.

UK context and accuracy

Cash flow forecasting is not a statutory requirement, but it is good practice for any UK business. Tax payments (VAT, corporation tax, PAYE) are often the largest outflows after payroll; building them into your forecast with the correct due dates is essential. This article is for informational purposes only and does not constitute professional tax or financial advice. Please speak to a qualified accountant before taking action.

Frequently asked questions

What is a 13-week cash flow forecast?

A rolling 13-week forecast shows expected cash in and out for the next 13 weeks. Each week you add a new week at the end and update the rest so you always have 13 weeks of visibility.

How do I forecast when customers will pay?

Use your average time to pay (e.g. 30 or 45 days from invoice). Apply that to your sales pipeline or invoicing plan. If payment behaviour changes, adjust the assumption.

What if my forecast shows a negative balance?

That is the value of the forecast: you see it before it happens. You can then cut non-essential spend, chase receivables, delay a payment (with agreement), or arrange a loan or overdraft.

Should I include VAT in my cash flow forecast?

Yes. VAT is a major flow. If you are VAT registered, include the VAT you expect to pay or receive in the month or quarter it hits the bank.

How does this differ from a budget?

A budget is a plan for revenue and costs (often for the P&L). A cash flow forecast is a plan for actual cash in and out. They are related but different: you can be on budget and still have a cash crunch if timing is wrong.

Summary and next steps

A cash flow forecast for your small business in the UK helps you see when money is coming in and going out, so you can avoid shortfalls and plan for tax and other big payments. Keep it simple: cash in, cash out, opening and closing balance. Update it regularly (e.g. a 13-week rolling forecast) and use it to make decisions.

If you would like help building or maintaining a cash flow forecast, we would be glad to help. At Figures Chartered Accountants we work with UK founders and small businesses on cash flow, management accounts, and planning. You can book a discovery call or look at our Management Reporting and Cash Flow Management services.