Business Cash Flow Forecast Calculator — the United Kingdom 2026-27
A month-by-month cash balance from turnover, costs and their growth rates — with the lowest point it reaches, the first month it goes negative, the VAT you will owe each quarter and the tax provision on positive months.
Each month turnover and costs grow at their own rate, the difference is the operating cash flow, and the balance carries forward.
| Start | £20,000.00 |
|---|---|
| M1 | £32,960.00 |
| M2 | £46,746.00 |
| M3 | £61,375.00 |
| M4 | £76,864.00 |
| M5 | £93,229.00 |
| M6 | £110,488.00 |
| M7 | £128,660.00 |
| M8 | £147,762.00 |
| M9 | £167,814.00 |
| M10 | £188,833.00 |
| M11 | £210,840.00 |
| M12 | £233,853.00 |
| M1 | £16,000.00 |
|---|---|
| M2 | £17,020.00 |
| M3 | £18,060.00 |
| M4 | £19,122.00 |
| M5 | £20,204.00 |
| M6 | £21,308.00 |
| M7 | £22,434.00 |
| M8 | £23,583.00 |
| M9 | £24,755.00 |
| M10 | £25,950.00 |
| M11 | £27,169.00 |
| M12 | £28,412.00 |
| M0 | £20,000.00 |
|---|---|
| M1 | £32,960.00 |
| M2 | £46,746.00 |
| M3 | £61,375.00 |
| M4 | £76,864.00 |
| M5 | £93,229.00 |
| M6 | £110,488.00 |
| M7 | £128,660.00 |
| M8 | £147,762.00 |
| M9 | £167,814.00 |
| M10 | £188,833.00 |
| M11 | £210,840.00 |
| M12 | £233,853.00 |
How the cash flow forecast works
Each month turnover and costs grow at their own rate, the difference is the operating cash flow, and the balance carries forward. The forecast is the arithmetic; the value is in the two numbers under it — the LOWEST balance and the month it happens. A business that ends the year comfortably can still fail in month four, and an annual profit figure will never show you that. If you are VAT registered the model nets output VAT against input VAT and pays the balance quarterly, which is why the balance steps down every third month; this is the single most common reason a first cash-flow forecast is wrong, because the VAT collected sits in the account looking like working capital until the return is due. The tax provision sets aside Corporation Tax on positive months so the liability is not a surprise. Runway is opening cash divided by the monthly burn, and only means anything while costs exceed turnover.
Formula: balanceₙ = balanceₙ₋₁ + (revenueₙ − expensesₙ) − indirect tax due − tax provision · runway = opening cash ÷ (expenses − revenue)
UK Cash-Flow Forecast Notes
What this calculator projects
This calculator builds a month-by-month cash balance projection: starting with your opening cash, adding net cash flow each month (revenue minus expenses), with optional monthly revenue growth applied. It shows you your balance at months 3, 6, and 12, the lowest point reached, and flags if the balance ever goes negative.
Key terms
| Term | Definition |
|---|---|
| Net cash flow | Revenue received − expenses paid in that month |
| Opening balance | Cash in bank at the start of the forecast period |
| Closing balance | Opening balance + cumulative net cash flow |
| Runway | Months until cash runs out (if burning cash) |
| Cash burn rate | Monthly expenses minus revenue (if negative) |
| Working capital | Current assets minus current liabilities |
This is a simplified model
This calculator uses a straight-line monthly model with optional growth. Real cash flow forecasts should also include: timing differences between invoicing and payment (debtors/creditors), seasonal patterns, one-off expenses, capital purchases, loan repayments, and tax payments. Use the Advanced workings tab to see the full monthly schedule.
Cash flow vs profit Why profitable businesses run out of cashThe difference between profit and cash flow — and why it matters for UK businesses
The profit/cash gap
Profit is recognised when a sale is made (accrual accounting). Cash arrives when the customer pays. For UK businesses with 30–60 day payment terms, a business billing £100,000/month may not receive cash for 1–2 months after the work is done. Meanwhile, wages, rent, and suppliers demand payment within 7–14 days.
The growth trap
Rapid growth can destroy cash flow. Each month you sell more, you need more stock, more staff, and more working capital — but cash from those sales arrives weeks later. Many profitable, growing UK businesses have collapsed because they could not fund the gap between paying for growth and receiving payment for it.
Common causes of cash flow problems in UK SMEs
- Slow-paying customers (30–90 day terms)
- Seasonal revenue with year-round fixed costs
- Large unexpected expenses (equipment failure, legal)
- VAT obligations — collecting VAT in one quarter, remitting in the next
- HMRC tax bills (income tax, PAYE) arriving in lump sums
- Rapid growth requiring upfront stock and staffing investment
The solution: cash flow forecasting
A 12-month rolling cash flow forecast lets you see problems 3–6 months before they occur — giving you time to arrange a credit line, chase debtors, defer non-essential spending, or accelerate collections.
Practical strategies to improve business cash flow — debtor management, financing, and timing
Speed up collections
The most powerful lever. Reduce your average debtor days (DSO — Days Sales Outstanding). Strategies: invoice immediately on completion (not end of month); offer 1–2% early payment discount for payment within 7 days; use direct debit or card payment instead of bank transfer; follow up overdue invoices within 24 hours of due date; use invoice financing to receive 80–90% of invoice value the same day.
Slow down payments (where appropriate)
Negotiate extended payment terms with suppliers — 30 days instead of 7 days gives you 3 extra weeks of float. Pay on the due date, not before. Use a business credit card with 55-day interest-free period for regular supplier payments.
Invoice financing and debtor factoring
Invoice finance lenders (such as iwoca, Funding Circle, MarketFinance) advance 80–90% of the invoice value on the day of issue. The fee is typically 1–3% of invoice value per month. For businesses with long debtor terms or seasonal patterns, this can dramatically smooth cash flow.
Business credit line
Arrange a business overdraft or revolving credit facility before you need it — banks are reluctant to lend when you are in difficulty. A £50,000 line of credit at 10–15% per year costs only £5–7.50/day to hold unused and can be a business lifesaver when needed.
How VAT, PAYE, and income tax affect your cash flow forecast
VAT timing impact
If you are on quarterly VAT return lodgement, you collect VAT from customers monthly but remit it quarterly. This means for 3 months you hold money that is not yours — it must be available when the VAT return is due. Many businesses accidentally spend their VAT obligations. Set aside 10% of your VAT-inclusive revenue each month into a separate account.
PAYE withholding
If you have employees, you withhold tax from wages and remit it to The HMRC either monthly or quarterly. This is effectively a 0% interest loan from The HMRC — manage it carefully. Lodgement frequency depends on your withholding amount: large withholders (>£1 million/year) remit monthly; medium (>£25,000/year) remit monthly; small remit quarterly.
Income tax provisioning
Corporation Tax (19% small profits rate up to £50,000 of profit; 25% main rate with marginal relief to £250,000) and Income Tax for sole traders and partnerships must be provisioned monthly even though it is paid later — CT is due 9 months and 1 day after year end for most companies. A common rule of thumb: set aside 25–30% of net profit monthly into a separate tax reserve account.
Payments on account
Sole traders and partners make two payments on account each year (31 January and 31 July), each half of the prior year’s bill; companies outside the large-company regime pay CT 9 months and 1 day after year end. If profits fall, you can apply to reduce payments on account. Cash-flow forecasting should include these dates as outflows in the relevant quarters.
Frequently asked Frequently asked questions
Why is cash flow more important than profit for UK businesses?
A profitable business can fail if it runs out of cash. Profit is an accounting concept — it is recognised when a sale is made. Cash arrives when the customer pays, which can be 30–90 days later. Meanwhile, wages, rent, and suppliers must be paid weekly or monthly. Cash flow forecasting prevents situations where a profitable business cannot make payroll.
What is a healthy cash reserve for an UK business?
Financial advisers generally recommend 3–6 months of operating expenses as a cash reserve. For a business spending £35,000/month, that is £105,000–£210,000. If you cannot hold that much, a pre-arranged line of credit provides a safety net. Also consider that VAT and tax obligations require set-asides — these are not discretionary cash.
How do I calculate business runway?
Runway = Current cash balance ÷ Monthly burn rate. Burn rate = monthly expenses minus monthly revenue (if spending more than you earn). A business with £50,000 cash burning £5,000/month has 10 months runway. If revenue equals or exceeds expenses, runway is infinite. For startups or declining businesses, monitoring runway is critical — you need to take action while you still have months remaining, not weeks.
How should I handle VAT in my cash flow forecast?
Use VAT-exclusive figures for revenue and expenses in your cash flow model — VAT is a flow-through item. However, add your quarterly VAT return payment as a separate cash outflow in the relevant month (the month your VAT return is due). The easiest way to manage VAT cash flow is to transfer 10% of every VAT-inclusive customer payment into a dedicated VAT return account on the day it arrives.
Where these figures come from
Business figures on this page are drawn from HM Revenue & Customs (corporation tax, VAT, PAYE), Companies House (company registrations), and GOV.UK (statutory employer and business obligations).
- Corporation Tax rates — GOV.UK — Corporation Tax rates and reliefs.
- VAT rates (standard 20%) — GOV.UK — VAT rates.
- PAYE & employer obligations — GOV.UK — PAYE and payroll for employers.
- Company registration & filing — Companies House — GOV.UK.
- Business rates — GOV.UK — Business rates.
Last checked: April 2026. Rates and thresholds are reviewed against the source of record each November, when annual adjustments for the following tax year are published.
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£50k revenue · £35k expenses · £20k opening Month 12: £219k · always positive
Starting with £20,000 cash, £50,000 monthly revenue, £35,000 expenses (net £15,000/month), 2% monthly revenue growth. Month 12 balance: £219,000. Cash never goes negative. Profit margin: 30%.
| Opening cash | £20,000 |
|---|---|
| Month 1 net cash flow | £15,000 |
| Month 12 balance | £219,000 |
| Lowest balance | £20,000 (Month 0) |
| 12-month total revenue | £678,000 |
| 12-month total expenses | £420,000 |
- Annual net cash generated £199,000
- Growth impact (2%/month) +£19,000 vs flat revenue
- Cash reserve ratio Month 12: 6.3× monthly expenses
- Working capital needs No external funding required
- Tax provisioning Set aside ~25% of net for income tax
£30k revenue · £28k expenses · £10k opening — tight cash Month 6: £15k · watch closely
Starting with £10,000 cash, £30,000 revenue, £28,000 expenses (net £2,000/month). With 3% monthly growth, by Month 6 the balance is approximately £15,000. The first 3 months are tight with only £2,000/month buffer.
| Opening cash | £10,000 |
|---|---|
| Month 1 net | £2,000 (thin margin) |
| Month 3 balance | £16,300 |
| Month 6 balance | £25,800 |
| Month 12 balance | £57,000 |
| Risk | Any unexpected cost could cause shortfall |
- Recommended buffer £84,000 (3 months expenses)
- Current buffer (Month 0) £10,000 = 10 days expenses
- Consider line of credit £20,000 facility as safety net
- Accounts receivable focus Chase invoices — 1 day faster = +£1k cash
- Growth adds £870/month extra by Month 6 Compounds benefit significantly
Cash flow vs profit — why they differ Profitable businesses can still run out of cash
A business can be highly profitable but cash-poor. Common causes: stock purchases paid before sales collected, long debtor payment terms, seasonal patterns, rapid growth requiring upfront investment, and one-off capital purchases.
| Revenue recognised | When invoice issued (accrual) |
|---|---|
| Cash received | When customer pays |
| Common gap (UK SMEs) | 30–90 days (debtor terms) |
| Expenses often paid sooner | Rent, wages, suppliers on 7–30 days |
| Seasonal businesses | Cash gap can be 3–6 months |
| Growth trap | More sales = more upfront costs before cash in |
- Solution 1 Invoice financing / debtor factoring
- Solution 2 Business credit card (interest-free days)
- Solution 3 Negotiate longer supplier payment terms
- Solution 4 Shorten debtor terms (offer early payment discount)
- Key metric Days Sales Outstanding (DSO) — track monthly
Business runway — how long your cash will last Runway = cash balance ÷ monthly burn rate
Runway is how many months your business can operate at current burn rate (expenses minus revenue) before running out of cash. Critical for startups and businesses in a downturn.
| Runway formula | Cash balance ÷ monthly burn |
|---|---|
| £20,000 cash, £5,000 burn/month | 4 months runway |
| £20,000 cash, £2,000 burn/month | 10 months runway |
| Profitable business | Infinite runway (generating cash) |
| HMRC debt risk | Tax obligations can accelerate burn |
| Healthy runway target | 6+ months for stable business |
- Ways to extend runway Cut costs, raise prices, collect debts faster
- Government support HMRC payment plans available if tax is due
- Business credit line £20k–£100k — negotiate before you need it
- Invoice finance Get paid 80–90% of invoice on day of issue
- Last resort Director loans, external investment, asset sales
Worked examples
| Inputs | Closing balance (final month) | Note |
|---|---|---|
| 50,000 revenue against 35,000 of costs, growing 2% a month | £218,012 | closes the year at 218,012 |
| Costs growing as fast as revenue | £173,904 | growth on both sides is much less valuable than it looks |
| Spending more than you earn | -£70,000 | a five-month runway, and the balance goes negative in month six |
The sources behind this calculator
- Corporate Finance Institute — EBITDA — why EBITDA is a non-GAAP measure with no single definition
- US SEC — Non-GAAP Financial Measures, Compliance & Disclosure Interpretations — the disclosure rules that exist precisely because EBITDA is not standardised
- Financial Reporting Council — the UK accounting and audit regulator
Last checked: September 2026. These are standard management-accounting definitions; where a term has no single agreed definition, the page says so.