Plug in your profit. See exactly what you owe HMRC.
Your taxable profit is your total business income minus allowable expenses. From that, HMRC deducts your personal allowance (£12,570 for 2026/27 — frozen until at least 2028). The remainder is taxed in bands: 20% basic rate on the first £37,700 (up to £50,270 total), 40% higher rate from £50,271 to £125,140, and 45% additional rate above £125,140.
Self-employed people pay Class 4 NI on profits between £12,570 and £50,270 at 6%, and 2% on profits above £50,270. Class 2 NI (£3.45/week) was abolished as a compulsory payment from April 2024 — you can still pay voluntarily to build up state pension entitlement. This calculator includes Class 4 automatically.
If your adjusted net income exceeds £100,000, your personal allowance is reduced by £1 for every £2 over £100,000. At £125,140 the personal allowance is zero. This creates an effective 60% marginal rate between £100,000 and £125,140 — a trap many growing businesses fall into.
Claim every allowable expense — materials, tools, mileage (45p/25p AMAP rates), insurance, phone, workwear. Consider pension contributions (reduce taxable income). If your profits regularly exceed £50,270, consider incorporating as a limited company and paying yourself via salary and dividends — speak to your accountant.
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