UK Small Business Costs: From Startup Capital to Break-Even

What it actually costs to start

UK startup costs vary enormously by ambition and structure, but rough bands hold up well: a bare-bones sole-trader launch with minimal marketing runs roughly £1,500-£4,000; a limited company with some software and marketing spend lands around £4,000-£12,000; and a fuller launch with comprehensive branding, a custom-built website and part-time staff can exceed £12,000. Company formation itself is cheap — £50-£78 to register with Companies House — but legal advice, a website, branding and marketing are where costs escalate.

The monthly profit equation

Once trading, the business's health each month reduces to one line: profit = revenue − (fixed costs + revenue × variable cost %). Fixed costs — rent, salaries, software subscriptions, insurance — are paid whether or not a single sale happens. Variable costs — materials, packaging, payment-processing fees, shipping — scale directly with revenue as a percentage.

monthly_profit = monthly_revenue − (fixed_costs + monthly_revenue × variable_cost_pct)
cumulative_cash[m] = cumulative_cash[m-1] + monthly_profit[m]
monthly_revenue[m+1] = monthly_revenue[m] × (1 + growth_rate)

Revenue itself is modelled as compounding at a chosen monthly growth rate rather than jumping straight to a steady-state figure — a far more realistic shape for an early-stage business gradually acquiring customers than assuming full-scale revenue from day one.

Reading the break-even month

The break-even month is the first month the cumulative cash balance — starting capital plus every month's profit or loss since — crosses back to zero or above, not simply the first month monthly profit turns positive. A business can be profitable every single month and still be technically "under water" for a long stretch while it works off an initial capital drawdown; the cumulative curve, not the monthly one, is what matters for solvency.

Ongoing costs that compound the picture

Corporation tax currently sits at 19% on profits up to £50,000 and 25% above that for limited companies. National Insurance contributions run around 13.8% of gross pay on top of any salaries, and VAT registration becomes mandatory once turnover crosses £85,000. None of these appear as separate line items in this simplified cash-flow model, but they are exactly the kind of ongoing cost that erodes the margin between the fixed-cost and variable-cost-percentage sliders in practice — a business modelled here as comfortably profitable can look very different once tax, National Insurance and compliance overhead are layered on top.

Frequently asked questions

Try it live

Everything above runs in your browser — open Small Business Cost Model and change the parameters while it is running. Nothing is installed, nothing is uploaded, the whole model lives in one tab.