Sole Trader Tax Calculator 2026-27

Sole trader profits are taxed as personal income through the Self Assessment system. Your taxable profit is calculated as total business income minus allowable business expenses (materials, travel, insurance, professional fees, a proportion of home costs if you work from home, and capital allowances on equipment). This net profit figure is then combined with any other income to determine your total taxable income for the year.

Income Tax is charged in bands after deducting the £12,570 Personal Allowance: 20% basic rate on income from £12,571 to £50,270, 40% higher rate from £50,271 to £125,140, and 45% additional rate above £125,140. The Personal Allowance reduces by £1 for every £2 earned above £100,000, creating an effective 60% marginal rate between £100,000 and £125,140. Tax is paid in two Payments on Account (January and July) plus a balancing payment in the following January.

National Insurance adds a further layer: Class 2 contributions are £3.45 per week (£179.40 per year) when profits exceed the Small Profits Threshold of £6,725. Class 4 contributions are 6% on profits between £12,570 and £50,270, then 2% on profits above £50,270. Both classes are collected through Self Assessment. Sole traders may also claim the £1,000 trading allowance instead of actual expenses if their total trading income is low, which exempts the first £1,000 from tax entirely.

Sole trader registration and first steps. Register as self-employed with HMRC by 5 October following the tax year you start trading. Failure to register: £100 penalty + interest. You'll get a Unique Taxpayer Reference (UTR) number — essential for filing Self Assessment. Choose accounting method: cash basis (simpler, suitable for turnover under £150k) records income when paid; accruals basis records income when invoiced. Cash basis is generally easier for sole traders.

Allowable business expenses — what you can claim. Office costs (rent, business rates, stationery, phone), travel (mileage 45p/25p HMRC rates, train, parking but NOT regular commute), clothing (uniforms only, not normal clothes), staff costs, things you buy to sell, financial costs (insurance, bank charges), business premises rates and utilities, marketing and entertainment (clients only). Use of home as office: £6/week simplified method OR actual proportional costs (% of bills based on rooms used and time).

Trading allowance — the £1,000 freebie. If your gross trading income is under £1,000/year, you don't need to register with HMRC at all (the trading allowance covers it). Between £1,000-£90,000 turnover: you can claim either actual expenses OR the £1,000 allowance — whichever is bigger. Useful for casual side hustles, online selling. Above £90k turnover: must register for VAT regardless of profit.

Class 4 NI changes — Class 2 abolished. From 6 April 2024, Class 2 NI (the flat £3.45/week if profits exceeded £12,570) was abolished. Self-employed now pay only Class 4 NI: 6% on profits £12,570-£50,270, then 2% above. Important: you still receive NI credits for State Pension as long as profits reach the Small Profits Threshold (£6,725). Effectively saves most self-employed people £179.40/year — a rare simplification of UK tax.