Most businesses don't fail because they're unprofitable. They fail because they run out of cash in a month their accountant told them was 'good'. A cashflow forecast is the antidote — and it doesn't need to be sophisticated. The template below is the model we use with founders, broken down into the inflows and outflows that catch people out.
Direct answer
Profit is opinion, cash is fact. A simple monthly forecast — what's coming in, what's going out, and what's left — is the single most useful spreadsheet a UK business owner can keep. Use the key facts, step list and official source links on this page to confirm the decision before you spend money or register anything.
12-month cashflow model (paste into a spreadsheet)
Section 01
How to use this template
- Copy into a spreadsheet (Numbers, Excel or Google Sheets).
- Replace the example figures with your own monthly forecast.
- Update actuals at month-end and roll the forecast forward.
- Track variance — anything more than 15% off forecast is worth understanding.
Section 02
The line items most people forget
- VAT — quarterly lump sums that can be 20% of inflows. Easiest cashflow killer.
- Corporation Tax — annual, due 9 months after year-end.
- Self Assessment payments on account — 50% of last year's bill in January and July.
- Employer NI on salaries — 15% on top of gross pay (2025/26 rate).
- Pension auto-enrolment contributions.
- Annual subscriptions billed once a year — domain renewals, accounting software upgrade.
Section 03
Three rules for a useful forecast
- Be pessimistic on sales. Multiply your gut forecast by 0.7 for the first six months of any new business.
- Be generous on costs. Round every line up, and add a 10% contingency line.
- Forecast cash, not invoices. The day money lands matters more than the day you billed.
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