Useful next calculations
Rates and sources
UK company rates (Corporation Tax, VAT, payroll NI) as published by HMRC and Companies House.
Source: HMRC — Running a business. Check the linked guidance and any live quote before acting.
When to use this calculator
- Before pricing a job, setting margin targets or reviewing hiring costs.
- When you want to test sensitivity around volume, tax, markup or overheads.
- When you need a practical estimate before committing to a budget or proposal.
- When you are modelling break-even volume as costs or prices change.
A worked example
These are the example figures the calculator opens with.
| Input | Value |
|---|---|
| Monthly Revenue (£) | £20,000 |
| Cost of Goods Sold (£) | £8,000 |
| Operating Expenses (£) | £5,000 |
| Tax Rate (%) | 20% |
For those figures the calculator returns:
- Net cash flow: £5,600.00
- Revenue: £20,000.00
- Gross profit: £12,000.00
- EBIT: £7,000.00
- Tax: £1,400.00
- Gross margin: 60.00%
Method & assumptions
This calculator produces a rolling cash flow forecast by taking your opening bank balance, adding projected cash receipts from sales, and deducting cash payments for costs in each period. Enter figures as cash amounts — that is, money you actually expect to receive or pay in the period, not accruals or invoices raised. VAT-registered businesses should include the VAT element in both receipts and payments and show the net VAT settlement as a separate line in the period it falls due.
The model does not incorporate capital expenditure, loan repayments, or tax liabilities unless you add them explicitly. It is a planning tool and will only be as accurate as the assumptions you feed into it. Review and update your forecast monthly against actuals to keep it useful.
Common mistakes
- Using optimistic assumptions without testing a more cautious scenario.
- Using revenue in place of gross profit when calculating margin.
- Treating the result as a final quote instead of a planning estimate.
- Forgetting employer on-costs when modelling the true cost of a hire.
What to do next
- Try at least one more scenario so you can compare a realistic range.
- Use the related calculators below to cross-check the decision from another angle.
- Write down the key outputs from your best scenarios before you decide.
- If the result surprises you, change one input at a time to isolate the driver.